PEP8: run travis checks

- Use a subset of PEP8 checks like in Toolkit
- Add make pep8
- Add pep8 checks to travis
PEP8: W601 .has_key() is deprecated, use 'in'
PEP8: E261 at least two spaces before inline comment
PEP8: E262 inline comment should start with '# '
PEP8: E271 multiple spaces after keyword
PEP8: W293 blank line contains whitespace
PEP8: E203 whitespace before ','
PEP8: E231 missing whitespace after ','
PEP8: E225 missing whitespace around operator
PEP8: E251 unexpected spaces around keyword / parameter equals