Merge pull request #1 from elenagr/master

Added code which computes collocations in a random sample of the full co...
createdb modified to include stemming and tokenization
Included a more elaborated collocations search including bigrams and trigrams.  TODO: Print the whole list of collocations. Currently both methods are run, we need to choose one and comment or remove the other.

Merge remote-tracking branch 'upstream/master'