setup: Simplify release process using "versioneer"

Release process is now as simple as tagging a release, there
is no need to manually updates version in __init__.py and setup.py

Most of the files enabling this process have been generated and/or
updated after:
1) pip install versioneer
2) adding "versioneer" section to setup.cfg
3) running "versioneer install"

For more details, see https://github.com/warner/python-versioneer/

Author: jcfr

Diff for: .gitattributes

@@ -0,0 +1 @@
+cmake/_version.py export-subst

Diff for: MANIFEST.in

@@ -2,3 +2,5 @@ include CMakeLists.txt
 include requirements-dev.txt
 
 recursive-include src *
+include versioneer.py
+include cmake/_version.py

Diff for: cmake/__init__.py

@@ -3,6 +3,11 @@
 import subprocess
 import sys
 
+from ._version import get_versions
+
+__version__ = get_versions()['version']
+del get_versions
+
 CMAKE_DATA = os.path.join(os.path.dirname(__file__), 'data')
 
 if platform.system().lower() == "darwin":