Client API now sync and async.

All operations now can be called either synce or async. The
sync call simply waits on the future returned from the async
call.
Add async command to RiakClient

Forgot to expose it to the end user :-D
Call correct method.

Oops.
Merge branch 'develop' into user-api-async

Conflicts:
	src/main/java/com/basho/riak/client/operations/FetchDatatype.java
	src/main/java/com/basho/riak/client/operations/UpdateDatatype.java