Hierarchy subtrees and supertrees
Basic testing and a sample .hxg file
Working densify method. It feels like a suboptimal implementation, will change it eventually
better implementation of densify
Now with caching to speed up the sparsify and densify process
Merge pull request #1 from xiaoling/master

gitignore, maven, and a new test case
comment changes
Integrating the tests into one file
Changing the gitignore for my convenience
creates a separate test code directory and adds a few test cases