Implement #6 (add a Yac::add method)
We need double ensure the value is right
Add functional style APIs
Hold on, do we really need them?
Move crc to key space, then we can save a dup hash stored
Skip reason
Add an double check in value
Revert "Add an double check in value"

Need some fresh air...

This reverts commit c96bcd63f64d072d92bf4583342115007736dfbb.
Reduce of the confilict possiblity
Use macros
change key max length to 48
Update README.md