ENH: add plot epochs function

COSMITS
ENH: add bad channels in red -- bug / working?
ENH+FIX: big cleanup

ENH+FIX: big cleanup2
COSMITS+ENH: improve readbility + trellis function

COSMITS+FIX
COSMITS...
ENH+API: fix+cleanup trellis
COSMITS
ENH: misc fixes
ENH: remove tests
ENH: support default epoch_idx + settle tight_layout
Merge pull request #741 from dengemann/plot_epochs

ENH: add plot epochs function and improve Trellis plotting