add set_key_range command(for KV)
udpate
add get_key_range
store key_range in meta_db
include replication stats in info
fix countbit without args bug
*incr commands return error if value cannot be converted to integer
update Changelog
Merge pull request #487 from ideawu/dev

		- *incr commands return error if value cannot be converted to integer(2014-10-24)
		- Include replication/sync stats in info(2014-10-23)
		- Add set_key_range, get_key_range(for KV) command(2014-10-22)