Function ngramsFinder() is now external and can be access from outside this code. It takes a text and finds the best bigrams and trigrams which are written into a file.

TODO: implement ngramsText() which takes a text and returns the text where the bigrams and trigrams have been converted to a single token
Added a new function in collocations which takes a text and process it joining the bigrams and trigrams stored in a external file.
Defined all related function and ngrams.py
TODO: remove the functions from collocations and import the ngrams.py file
Cleaning up and writing comments
Merge pull request #6 from elenagr/master

ngrams