setup: Add __version__ attribute for the tasklib module

Providing __version__ attribute is a reasonably common convention among
packages in the Python ecosystem. Currently the only other reliable
alternative is to use pkg_resources.get_distribution method, however,
importing pkg_resources is notoriously slow [1,2].

Provide the __version__ attribute to provide an API interface to check
the version of tasklib at runtime.

Bump the version in order to reflect module API change.

[1] pypa/setuptools#510
[2] pypa/setuptools#926

Author: tbabej

setup.py

@@ -2,7 +2,7 @@
 
 install_requirements = ['pytz', 'tzlocal']
 
-version = '2.2.0'
+version = '2.2.1'
 
 try:
     import importlib

tasklib/__init__.py

@@ -1,3 +1,5 @@
 from .backends import TaskWarrior
 from .task import Task
 from .serializing import local_zone
+
+__version__ = '2.2.1'