Add pep8 config, use pep8 in travis

also, fix E111-E113 errors:
E111 - indentation is not a multiple of four
E112 - expected an indented block
E113 - unexpected indentation

That doesn't say we can't use the previous stable version.
It just says we can't use 1.5.7.

I'm proposing to use 1.5.6, and stick with it until we decide that some future revision of pep8.py fits our needs better.