added BTGComputation test

* test for two master vertices
* fixed typos
adding changes from aggregation branch
adding changes from aggregation branch
removed unnecessary files
Merge branch 'aggregate' into biiig-testing
Merge branch 'aggregate' into biiig-testing

Conflicts:
	giraph-examples/src/test/java/org/apache/giraph/examples/biiig/BTGComputationTest.java