* Move StringStore class to its own file
* Refactor, move Lexeme struct to structs.pxd
* Move all struct definitions to structs.pxd, to avoid circular dependencies
* Rename Lexicon to Vocab, and move it to its own file
* Update tokens.pyx as part of reorg
* Refactor morphology.pyx
* Export set_morph_from_dict function
* Move tokenizer to its own file, and refactor
* Rename lang.pyx to tokenizer.pyx
* Move murmurhash to .pxd in strings file
* Move lang.pyx to tokenizer.pyx
* Import slice_unicode from strings.pyx
* Tmp
* Everything compiling after reorg. About to start testing.
* Add vocab.pyx to setup, and ensure we can import spacy.en.lang
* Add attrs file for English
* More index.rst fiddling
* Upd tokenizer test
* Upd contractions test
* Upd emoticons test