Merge pull request #14 from cemerick/master

Miscellaneous enhancements
Fix / improve dynamodbv2 value data type support:

* Accept any number (not just integers)
* Return longs or doubles from gets, as necessitated by values'
  string representation
* Add support for binary and binary set values (byte[] or ByteBuffer
  values are accepted; ByteBuffers are returned per the AWS SDK)