Pig support for hadoop CqlInputFormat

Patch by Alex Liu, reviewed by brandonwilliams for CASSANDRA-6454
Merge branch 'cassandra-2.0' into cassandra-2.1.0
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Pig support for hadoop CqlInputFormat

Patch by Alex Liu, reviewed by brandonwilliams for CASSANDRA-6454