Update pep8 (1.4.5 -> 1.4.6) and pyflakes (0.7.2 -> 0.7.3)

Pep8 now honors the `# noqa` comment, which disables pep8 checks for a
certain line (see jcrocholl/pep8#180).

This is useful for SQLalchemy `== None` filter comparisons and used all
quite a bit in Adhocracy model methods, so this should reduce our pep8
error counter quite a bit.