Autopep8

I used [autopep8](https://github.com/hhatto/autopep8) to make all of pandas py files PEP8 compliant (Excluding `E501 lines too long` (over 80 chars), and around 6 changes which had to be reverted to fix test failures - see second commit). *Generated py files  are not compliant.*

I iterated over every py file in the package using [autopep8](https://github.com/hhatto/autopep8), then inspected the output of [pep8](https://github.com/jcrocholl/pep8) to drill-down to find any compliance issues which may change the meaning of the code (and hence needed to be considered individually).

I haven't included a unittest for PEP compliance using pep8.

For me this passes all the same tests as the master branch.

*Since this affects such a large set of the code it may not be reasonable to pull, however it is certainly a proof of concept.*