Switch to "-SNAPSHOT" based versioning
Don't print anything by default
Stop using a data_readers.clj

Since the serialization format only matters when the library itself
calls read, we can set the data readers there instead of having a
global file.

This is halfway cleaner. The other half we can't easily avoid is
defining print-method for different types.
Version 0.4.0
Update docs
Prepare for next release cycle