Pyss3

Added
- Live Test: layout updated.
- PySS3 Command Line: ``frange`` function added as an alias of ``r`` for the ``grid_search`` command.

Fixed
- PySS3 Command Line: live_test always lunch the server with no documents (even when before "live_test a/path")
- Live Test:sentences starting with "unknown" token were not included in the "Advanced" interactive chart

Fixed
- Server: fixed bug that stopped the server when receiving arbitrary bytes (not utf-8 strings)
- PySS3 Command Line: fixed bug when loading live_test with a non existing path
- Live Test: now the user can select single letter words (and are also included in the "advanced" live chart)

Added
- Summary operators are not longer static.
- ``Server.set_testset_from_files`` lazy load.

Fixed
- Evaluation plot: confusion matrices size when working with k-folds

Added
- `Dataset` class added to `pyss3.util` as an interface to help the user to load/read datasets. Method `Dataset.load_from_files` added
- Documentations updated

Added
- PySS3 Command Line Python 2 full compatibility support

Fixed
- Matplotlib set_yaxis bug fixed

Fixed
- Dependencies and compatibility with python 2 Improved