ENH: add condition count to Epochs __repr__

This in part addresses #338
ENH: more efficient count, break after 30 chars + add '...'
COSMITS
ENH: condition names as strings
ENH: endles list at the end + newline
ENH: raw string formatting
FXI: tutorial.rst
Merge pull request #459 from dengemann/epochs_repr_count

ENH: add condition count to Epochs __repr__