In this commit the following changes have been done:

1- Updated README to be more informative
2- Fixed a classpath bug in scalac-plugin.xml file
3- Added a bit of functionality for HPE.scala file, so I can test it. and updated the signature of feval to return the produced tree as well.
4- Added a test case, a simple one (just to know if the plugin works at all)
5- Created a test script, which automatically tests the plugin against the non-plugin version