PARQUET-89: Add hadoop-2 test profile for travis CI.

This also fixes problems that prevented hadoop-2 from passing:
* Dynamically resolve counter methods in parquet-hadoop
* Parameterize pig version with hadoop-2 support
* Update pig test for hadoop-2 change (no nulls allowed)
* Update parquet-hive to depend on hadoop-client

The parquet-test-hadoop2 module has been removed because the test is no
longer needed. It was a copy of TestInputOutputFormat from
parquet-hadoop that is now run when that module is tested.

The travis config will now run each test profile in a different run.