* upgrade gmock to 1.7.0
 * Extract common index operations to IndexImpl
 * Dont allow to call HashIndex::insert/erase/search directly.
 * cleanup unused functions
 * remove duplicated code in range_index
 * move split_index to index_impl
 * reorder
Merge pull request #1 from eddyxu/hash_index

Extract shared functions from Hash/Range index to IndexImpl
 - remove unused structure and function signatures
 + Start to write C++ version of VSFS API
 * Added more interfaces
 * sync with the newest cpplint.py
 * reformating
 * basic build and test blocks for C++ API
 * simplify api
 * skeleton of vsfs api test
 * Added missing vsfs.cpp
 * mock connection
 * added missing interfaces
 * import VSFS EC2