Removes completed TODO re: scientific Python
Adds Sphinx to requirements.txt
copy edit structure.rst
Merge pull request #283 from geraldarthur/master

copy edit structure.rst
Fix link to Dive Into Python 3
minor formatting changes.
Rewrite section on choosing a Python version
Merge pull request #287 from untitaker/python2vs3

Rewrite section on choosing a Python version
[+] Scenarios: CLI: Added docopt description.
Merge pull request #288 from moigagoo/master

Added a reference to docopt, a very useful package for creating command line interfaces
Merge pull request #286 from artloder/minor-changes

Minor formatting changes.
Merge pull request #285 from puppe/patch-1

Fix link to Dive Into Python 3
Merge pull request #284 from kuyan/master

Grammar, capitalization fixes
Merge pull request #282 from lyndsysimon/master

Housekeeping
Fix link to tox documentation.
Merge pull request #290 from rvanlaar/patch-1

Fix link to tox documentation.
Fix enumerate code snippet to run without error message

Code previously added numbers to strings, which results in a TypeError
Merge pull request #292 from mattboehm/master

Fix enumerate code snippet to run without error message
Added note on Python 3 and Pillow.