* Remove taggers from Language class. Work on doc strings
* Revise intro copy. Add NLTK comparison
* Add tokenizer section
* Make intro chattier, explain philosophy better
* Rename Lexicon._dict to Lexicon._map
* Work on get_array method of Tokens
* Make StringStore.__getitem__ accept unicode-typed keys.
* Fix bug in refactored StringStore.__getitem__
* Make flag-setting a language-specific thing
* Hack Tokens to work without tagger.pyx
* Move String struct stuff into the utf8string module, from spacy.lang
* Add typedef for attr_t. Change flag_t to flags_t
* Hack setup.py to exclude tagger stuff
* Introduce first attempt at const-ness
* const added to Lexicon interface. Seems to work.
* Make the string-store serve const pointers to Utf8Str
* Add STEM attribute to lexeme
* Add as_array and count_by method
* Hack Token class to take lex.dense inplace of the old lex.norm. This needs to be fixed...
* Fiddle with lexeme attrs