Add initial support for riak 2.0's bucket types
WIP support for 2.0 counter and set CRDTs
Implement CRDT maps, refactor some stuff
Refactor for better API
Implement datatype Destroy() and remove methods for map fields
Fix issues in NewBucketType reported by @MJDSys
Go fmt and adding `default` as type when using NewBucket
Merge branch 'nervcorp-adt-crdts'