+ added meta manager class and test case.
+ added persistent storage using leveldb
* updated vobla version.
+ added have function
+ added test case for init
* updated copyright comment for meta manager test
* updated according to code review
* updated comments
* changed all uint64_t to int64_t
* sorted header
* renamed the test case for search to TestSearch
* updated according to code review.
* added test case for insert failure
* added using unique_ptr in meta_manager.h
Merge pull request #14 from vsfs/add_meta_manager

Add meta manager