Removes completed TODO re: scientific Python
Adds Sphinx to requirements.txt
Correct spelling of 'aforementioned'.
Nitpicky rewordings and grammar fixes.
Add line breaks for conformance with the Style Guide.
GtK --> GTK
'many' --> 'much'
Merge pull request #283 from geraldarthur/master

copy edit structure.rst
PEP and Python are capitalized.
'async' --> 'asynchronous'
Code block type is 'console', not 'bash'.
Added note about OSX-GCC-Installer and Xcode conflict.
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