* Shift index.hashes and index.lexicon to PointerMap, instead of Google dense_hash_map
* Switch tagger to PointerMap
* Switch Perceptron away from dense_hash_map, to PointerMap
* Adding new learner implementation. Still bugs.
* Memory errors fixed, but learning seems to have bugs.
* Add unit tests for new perceptron
* Fix bug in perceptron, add averaging
* Add serialization test, and fix serialization bug
* Bug fixes to new perceptron
* Working on bug in new perceptron
* Add thinc to setup, and remove sparsehash
* Zero scores array in new perceptron
* Switch tagger to use new perceptron
* Enable cython profiling for thinc.pyx
* Move ScoresCache to thinc.pyx
* Have tagger use weight-type from the learner
* Return the number of features seen, for use with the new perceptron
* Raise error if tag is empty string
* Upd parser test to use Input.from_untagged
* Remove old perceptron from setup