Remove free_long and free_double
Fix code style
Merge remote-tracking branch 'upstream/develop' into remove_free

Conflicts:
	jubatus/core/clustering/kmeans_compressor.cpp
Remove unnecessary serialize method
Refactor
Use partial_sort
Merge pull request #671 from jubatus/remove_free

Remove free_long and free_double
Rename mixable to deprecated_mixable
Add new model/mixable interface
Extract libjubatus_core module