Updated cassandra input and output adapters and added AbstractBatchTransactionableStoreOutputOperator

commit 77d0a427347ed0564dafee3ee00bfb226a0a4322
Merge: b29b248 1000a99
Author: Rohit Sharma <rohitsharma91@gmail.com>
Date:   Wed Jun 25 17:00:58 2014 -0700

    Merge branch 'master' of github.com:DataTorrent/Malhar into cassandra_adapters

commit b29b248d91e9f5036f29101e2971e99f5d31b286
Author: Rohit Sharma <rohitsharma91@gmail.com>
Date:   Wed Jun 25 16:59:57 2014 -0700

    Updated cassandra input and output adapters and added AbstractBatchTransactionableStoreOutputOperator

commit 7d91c018f9db718f0348cfe1d3a5925836cae131
Author: Rohit Sharma <rohitsharma91@gmail.com>
Date:   Tue Jun 17 19:39:33 2014 -0700

    MLHR-1172 and MLHR-1173 added cassandra input and output adapters