added tree-rnn to hold RNN structure during decoding
enlarged memory alignment size to at least 16
added tree-rnn feature
bugfix for network computation
erase features for zero values
simplified the implementation
added word embedding data structure and use it
added bi-tree for rnn
differentiate empty words
implemented tree-rnn over frontiers (but not tested)
added frontier-tree-rnn feature
prettify
added operators and removed random option
use of typename for multiplication
added more methods necessary for training
implemented tree-rnn learner (but not tested...)
removed dependence on lbfgs/cg-descent
use of 100 as rounding base
renamed the variable from the states in the antecedents
explicitly use the state pointer for copying