TrigramCollocationFinder.from_words with window

Added the option to create a trigram finder with windows_size
Removed inrelevat line 

the line was previously used for debugging
Corrected TrigramCollocationFinder.from_words with window

Now w1 is kept constant during itertools.combinations of words w2 and w3

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
new QuadgramCollocationFinder class

added functions _contingency and _marginals

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
temp commit -> git reset --soft 'HEAD^'

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
added with_window test for trigram finder
bugfixes: typo, making QuadgramCollocationFinder readable

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
added window to from_words in quadgram finder

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
new QuadgramAssocMeasures Calculates quadgram contingency table

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
removed un relevant file

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
merge from develop

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
removed old function

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
avoid MemoryError on large ngram_fd
added _marginals in QuadgramAssocMeasures

Signed-off-by: Ofer Helman <helmanofer@gmail.com>
PEP8: i:i+n clearer than i:i + n
using iteritems to iterate FreqDist instead of items
updated docstring QuadgramCollocationFinder
Merge pull request #640 from helmanofer/ofer_dev

Ofer dev
fixed failing semantics doctests