Python wrappers

[rth]

In order to use the python package as a drop in replacements of scikit-learn's text vectorizers we would need,

• [x] Wrap HashingVectorizer #1
• [x] Wrap CountVectorizer #14
• [ ] Implement most common functionality
• [ ] Pass scikit-learn tests (when they make sense).

[rth]

Closing, for now, we are relaxing a bit the condition to pass scikit-learn tests.