PEP8: add ignore E126 to tox.ini.  Changed from E121 in pep8 1.5

There were 910 errors for E126, which is too many to fix now.
PEP8: fix E111 and E113 (indentation unexpected / not a multiple of 4) errors.
PEP8: fix E112 ("expected indented block") errors.
PEP8: fix E129 ("visal indent same as next logical line") errors.
PEP8: fix E713/E714 ("not in", "is not") errors.
PEP8: fix E131 ("continuation line unaligned") errors.
MAINT: fix pyflakes issues.
MAINT: address review comments on gh-3512 by Warren and Denis.
Merge pull request #3512 from rgommers/travis-pep8

Fix PEP8 errors showing up on TravisCI after pep8 1.5 release