timestamp for trainer
Made it possible to load models in the training process 

(refer 54dd72584a5e77b713dc7b57eb4ffdac83b79ea1)
refactor increment left and right cube item
bug fix: bigram at root
an example language model and the oracle orderering, where the oracle
reordering is obtrained from word alignment
bug fix: bigram at terminal
bug fix: bigram for discontinuous hypothesis
bug fix: compute loss correctly
bugfix: bigram for discontinuous hypothesis
bug fix: compare hyper-edge's class as well
skip unnecessary hypothesis more
manage only unique permutations during search
bigram as a non-local feature (with bug fix when increment left and
right)
refactoring for non-local feature including bigram
bug fix: termininals may have bigram features