Function 'callable' has returned in Python 3.2
Divide evaluation methods by types
Strip sentences after tokenization
Raise exception if evaluated document is empty

It's better solution than to return zero. It's
users's resposibity to provide correct documents.
In fact is empty document a document?
Added TF model of document
Added cosine similarity evaluation #1

And this commit contains the 100th test, hooray :)
Python 2.6 doesn't support chained with statement
Added configuration for TravisCI