Update README with conda instructions.

Author: pavoljuhas

README.rst

@@ -46,7 +46,8 @@ http://diffpy.github.io/diffpy.srreal.
 REQUIREMENTS
 ------------------------------------------------------------------------
 
-The diffpy.srreal requires Python 2.6 or 2.7 and the following software:
+The diffpy.srreal requires Python 2.7, C++ compiler and
+the following software:
 
 * ``setuptools`` - tools for installing Python packages
 * ``NumPy`` - library for scientific computing with Python
@@ -58,62 +59,61 @@ The diffpy.srreal requires Python 2.6 or 2.7 and the following software:
 * ``diffpy.Structure`` - simple storage and manipulation of atomic structures
   https://github.com/diffpy/diffpy.Structure
 
-Recommended software:
+Optional software:
 
 * ``periodictable`` - periodic table of elements in Python
   http://www.reflectometry.org/danse/elements.html
 * ``pyobjcryst`` - Python bindings to ObjCryst++, the Object Oriented
   Crystallographic library for C++, https://github.com/diffpy/pyobjcryst.
 
-Some of the required software may be available in the system package manager,
-for example, on Ubuntu Linux the dependencies can be installed as::
+We recommend to use `Anaconda Python <https://www.continuum.io/downloads>`_
+as it allows to install all software dependencies together with
+diffpy.srreal.  For other Python distributions it is necessary to
+install the required software separately.  As an example, on Ubuntu
+Linux some of the required software can be installed using ::
 
    sudo apt-get install \
       python-setuptools python-numpy scons \
       build-essential python-dev libboost-all-dev
 
-For Mac OS X machine with the MacPorts package manager one could do ::
+To install the remaining packages see the installation instructions
+at their respective web pages.
 
-   sudo port install \
-      python27 py27-setuptools py27-numpy scons boost
 
-When installing with MacPorts, make sure the MacPorts bin directory is the
-first in the system PATH and that python27 is selected as the default
-Python version in MacPorts::
-
-   sudo port select --set python python27
+INSTALLATION
+------------------------------------------------------------------------
 
-For other required packages see their respective web pages for installation
-instructions.
+The preferred method is to use Anaconda Python and install from the
+"diffpy" channel of Anaconda packages ::
 
+   conda config --add channels diffpy
+   conda install diffpy.srreal
 
-INSTALLATION
-------------------------------------------------------------------------
+diffpy.srreal is also included in the "diffpy-cmi" collection
+of packages for structure analysis ::
 
-The easiest option is to use the latest DiffPy-CMI release bundle from
-http://www.diffpy.org, which comes with diffpy.srreal and all other
-dependencies included.
+   conda install diffpy-cmi
 
 If you prefer to install from sources, make sure all required software
 packages are in place and then run ::
 
-   sudo python setup.py install
+   python setup.py install
 
-This installs diffpy.srreal for all users in the default system location.
-If administrator (root) access is not available, see the usage info from
-``python setup.py install --help`` for options to install to a user-writable
-location.  The installation integrity can be verified by changing to
-the HOME directory and running ::
+You may need to use ``sudo`` with system Python so the process is
+allowed to copy files to the system directories.  If administrator (root)
+access is not available, see the output from
+``python setup.py install --help`` for options to install to
+a user-writable location.  The installation integrity can be verified by
+changing to the HOME directory and running ::
 
    python -m diffpy.srreal.tests.run
 
 An alternative way of installing diffpy.srreal is to use the SCons tool,
-which can speed up the process by compiling the C++ files in parallel (-j4)::
+which can speed up the process by compiling the C++ files in parallel (-j4) ::
 
    sudo scons -j4 install
 
-See ``scons -h`` for build parameters and options to install to a user-writable
-directory.
+See ``scons -h`` for decription of build targets and options.
 
 
 DEVELOPMENT
@@ -135,6 +135,25 @@ integrity, use ::
 
    scons -j4 build=debug develop [test]
 
+When developing with Anaconda Python it is essential to specify
+header path, library path and runtime library path for the active
+Anaconda environment.  This can be achieved by setting the ``CPATH``,
+``LIBRARY_PATH`` and ``LDFLAGS`` environment variables as follows::
+
+   # resolve the prefix directory P of the active Anaconda environment
+   P="$(conda info --json | grep default_prefix | cut -d\" -f4)"
+   export CPATH=$P/include
+   export LIBRARY_PATH=$P/lib
+   export LDFLAGS=-Wl,-rpath,$P/lib
+   # compile and re-install diffpy.srreal
+   scons -j4 build=debug develop
+
+On Mac OS X the distributed Anaconda packages are built for operating
+system version 10.6, which may be incompatible with codes compiled on a
+newer OS.  To avoid this problem set the environment variable
+``MACOSX_DEPLOYMENT_TARGET=10.6``.  This allows to build diffpy.srreal
+against the Anaconda package for the libdiffpy library.
+
 
 CONTACTS
 ------------------------------------------------------------------------