Upgrade pep8 module to latest

`ckan/migration/versions/066_default_package_type.py` is passing `test_coding_standards.py` for me locally, but [failing on Travis](https://travis-ci.org/okfn/ckan/jobs/8536093).

I have pep8 1.4.5 in my virtualenv but `dev-requirements.txt` has 1.3.3.

Also, the underlying issue is maybe that `066_default_package_type.py` has a random empty line at the top of the file: <https://github.com/okfn/ckan/blob/18313625003d4b4be5227a07dceff6c5a65674b1/ckan/migration/versions/066_default_package_type.py#L1>. Deleting this line makes the file pass with both versions of pep8.