update read me
update document
Add table of contents
Merge branch 'develop' of https://github.com/siddontang/ledisdb into develop
use go-log and adjust some param name

go-log now has a well document.
it can be used directly.

limit may cause confused, use count instead
adjust Open interface, not backwards compatibility
replication use snappy
optimize cgo leveldb

reduce memory copy, reduce cgo call number
bugfix: BufGet must make if b is nil
optimize BufGet
Optimize memory copy
elimination exec in new goroutine

check whether cog cpu is still very high
Merge branch 'develop'