Added a possibility to restrict Google Syn NGram corpus to only some of its parts (based on the ___.XXX-of-XXX.gz naming scheme of files)
Rewrote the train from syn ngrams function to take an iterator over text lines "govword depword dType count", rather than talk to the corpus instance itself. This allows me
to feed the training data from stdin or file, and is corpus-agnostic.
A multiprocessing based ngram generator which can produce the data for training much faster.