Add 'license' key to setup script

Author: xolox

setup.py

@@ -3,7 +3,7 @@
 # Setup script for the `vcs-repo-mgr' package.
 #
 # Author: Peter Odding <[email protected]>
-# Last Change: March 8, 2018
+# Last Change: April 26, 2018
 # URL: https://github.com/xolox/python-vcs-repo-mgr
 
 """
@@ -121,6 +121,7 @@ def have_environment_marker_support():
       url='https://github.com/xolox/python-vcs-repo-mgr',
       author="Peter Odding",
       author_email='[email protected]',
+      license='MIT',
       packages=find_packages(),
       entry_points=dict(console_scripts=[
           'vcs-tool = vcs_repo_mgr.cli:main',