REGULAAAAAAR EXPREEEESSSIIIIOOOOOONS. GO!

TODO nested sub signatures
TODO start
TODO flattening
Update python.html.markdown

Added more details to try/except section.
Update python3.html.markdown

Added more info to try/except. Corrected some trivial bugs.
Merge pull request #696 from Shashwat986/master

Updated python and python3 with try/except details
Update python.html.markdown

range() is not a generator in python 2.x
Merge pull request #698 from Shashwat986/patch-1

Update python.html.markdown
aded negative integer division
Merge https://github.com/adambard/learnxinyminutes-docs