Remove free_long and free_double
Fix code style
Write compressive storage test
Increment forgetting weight all of when carry up occurrs
Set forgetting_threshold in test
Merge remote-tracking branch 'upstream/develop' into remove_free

Conflicts:
	jubatus/core/clustering/kmeans_compressor.cpp
Remove unnecessary serialize method
Refactor
Use partial_sort
Fix jubatus servers to stop mixer before RPC server stopped

fixes #730
Merge pull request #704 from jubatus/fix-forget-weight

Fix behavior of forgetting_factor
Merge pull request #671 from jubatus/remove_free

Remove free_long and free_double
Merge pull request #732 from jubatus/fix-730

Fix jubatus servers to stop mixer before RPC server stopped
Add virtual dtor to clustering::storage
new feature unlearning
test compile ok, yet it does not success
append core/unlearn
add recommender_storage_base.hpp
Use unordered_map in inp function of local_storage instead of vector

The new key_manager uses unordered_map for id2key instead of vector.
We need to use unordered_map in inp method as the same way to calculate scores for all labels.
Write test for inp method after clear