Update travis to use miniconda3 not miniconda2

This travis file is now only used for deployment of 
conda builds, and I'm not sure if it works. But might
as well update this anyway.

Author: rwest

.travis.yml

@@ -15,8 +15,8 @@ stages:
 before_install:
   - cd ..
   # Install miniconda
-  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then wget http://repo.continuum.io/miniconda/Miniconda2-latest-Linux-x86_64.sh -O miniconda.sh; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then wget http://repo.continuum.io/miniconda/Miniconda2-latest-MacOSX-x86_64.sh -O miniconda.sh; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then wget http://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then wget http://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh -O miniconda.sh; fi
   - bash miniconda.sh -b -p $HOME/miniconda
   - export PATH=$HOME/miniconda/bin:$PATH
   # Update conda