* An initial impliment of log_manager.h
 + Added comments on the thrift file
 - remove dependancy of Protobuf
 * Remove protobuf lib checking and from README
 * Remove downloading protobuf in travis
Merge pull request #19 from vsfs/remove_protobuf

Remove deps of Protobuf
 * Sorted headers of log_manaer.h
 * Change LogRecord::buffer() to LogRecord::serialize()
Merge pull request #18 from vsfs/log_manager

 * An initial impliment of log_manager.h
* refactored index_server_manager to server_manager.
+ added server_manager files
* modification according to code review.
Merge pull request #20 from vsfs/server_manager

Server manager
 * Remove protobuf from common/Makefile
Merge branch 'master' into add_meta_server
+ added join_meta_server in master_controller
* fixed inconsistency in meta_controller.cpp