creates a separate test code directory and adds a few test cases

'mvn test' for testing; 'mvn compile' for compilation; and 'mvn package' to create a jar. Please set the test directory accordingly in eclipse.

Please use relative paths to files (e.g. use 'src/sample.hxg' in the testing code ).

See this gist for some serialization code : https://gist.github.com/xiaoling/7c0d43433ce09c8b4682