#26 Parameters for extracting collocations

[Sylvain Loiseau]

Some parameters may be added for extracting collocations :

- Co-frequency between node and collocate at least: n (default value eg 5)
- Frequency of the collocate at least: n (default value eg 5)
- selecting different statistic methods (hypergeometric, log-likelihood, Z-score, ...)

The first two seem very important for controlling the list of collocates. It would make this threshold an explicit choice.

The last one would at least make it possible to tell the user which method is currently used...