revamped fd rnns
updated rnn music notebook with fd-rnns
Added parameter to pad zeros from the left and right.
FIX: Fast Dropout Mlp was using wrong loss.
FIX: docs did not build correctly because auto summary was missing
minor doc fixes
Skip connections for rnns.
tests for rnns updated
auto encoder now has corrupted output in its .exprs
undid rectifier hotfixes
added todo
FIX: dropout for hidden to out connection was 
using parameter from hidden to hidden
fixed turning off variance propagation