fix bit_index_storage to erase rows with empty vector on MIX
fix bit_index and inverted_index erase rows locally
fix recommender get_all_rows distribution mode to random (fix #683)
replace map with unordered_map
Remove serialization methods for clustering
Make __repr__ function instead of __str__
Detect IO errors in save
Remove unnecessary logs
Devide open error and read/write error
Detect IO error in load
Remove incomplete file
Merge pull request #686 from jubatus/fix-683

fix recommender get_all_rows distribution mode to random (fix #683)
Merge pull request #694 from jubatus/replace-map

replace map with unordered_map
Set seeds of random values in clustering test case
Merge pull request #702 from jubatus/clustering-test-seed

Set seeds of random values in clustering test case
Merge pull request #696 from jubatus/python-repr

Make `__repr__` method instead of  `__str__`
mix number should be output as ordinal number fix #552
classifier: add `set_label` and `get_labels` for fix #655
cpplint ok
local_storage_mixture::set/get_label(s) is tested by `storage_test.cpp`