* Upd count_feats method, using what we learnt from lattice.
* Add greedy tagger module, for lattice parsing
* Revert to reserving 0 as a special index variable. Haven't properly checked whether this breaks things.
* Manage accuracy in non-batch update in perceptron
* Add init_words option to beam to reconcile nbest and lattice parsing
* Switch to greedy tagger. Some other subtle changes.
* Add lattice pruning
* Fix count_feats in nbest_parser
* Restore extra features for greedy tagger
* Adding lattice_factor argument to scripts