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

Seen that.
I'd suggest agreeing on a specific version, and upgrading only if the new version is an improvement for us.
"Specific version" could mean either referring to a specific download location, or simply copying it into SymPy's tree.