Add requirements.txt generated by 'pip freeze'.

.gitignore

 *.pyc
+bin
+include
+lib
+pip-selfcheck.json
+pyvenv.cfg
+

requirements.txt

+alabaster==0.7.7
+Babel==2.2.0
+docutils==0.12
+Jinja2==2.8
+MarkupSafe==0.23
+Pygments==2.1
+pytz==2015.7
+six==1.10.0
+snowballstemmer==1.2.1
+Sphinx==1.3.5
+sphinx-rtd-theme==0.1.9