Merge pull request #391 from dengemann/fix_plot_evoked_ylim

FIX: fix ylim kwarg
FIX: Dealing with tag=None in bad channels
Merge pull request #396 from Eric89GXL/raw-read-fix

FIX: Dealing with tag=None in bad channels

Thanks!
FIX: Adding viz tests
ENH: Adding test
Merge pull request #397 from Eric89GXL/viz-tests

FIX: Adding viz tests
ENH: Adding rank computing function
FIX: Adding to ref
FIX: Addressing comments
STY: Better variable naming
WIP: Moving toward improving match
FIX: Making inverse calculation more consistent
FIX: Dont want to set log level in test
FIX: Improving test coverage and old bug
STY: Better info
STY: Fixing colons
FIX: Allow re-calling of .as_diag()
STY: PEP8 and pyflakes
FIX: Making fixed orientation consistent
FIX: Better inverse matching