Setting timestamps in Cassandra transactions.
Merge branch 'master' of https://github.com/gwhitehawk/titan

Conflicts:
	titan-berkeleyje/src/main/java/com/thinkaurelius/titan/diskstorage/berkeleyje/BerkeleyJETx.java
	titan-cassandra/src/main/java/com/thinkaurelius/titan/diskstorage/cassandra/AbstractCassandraStoreManager.java
	titan-cassandra/src/main/java/com/thinkaurelius/titan/diskstorage/cassandra/CassandraTransaction.java
	titan-cassandra/src/main/java/com/thinkaurelius/titan/diskstorage/cassandra/astyanax/AstyanaxStoreManager.java
	titan-cassandra/src/main/java/com/thinkaurelius/titan/diskstorage/cassandra/embedded/CassandraEmbeddedStoreManager.java
	titan-cassandra/src/main/java/com/thinkaurelius/titan/diskstorage/cassandra/thrift/CassandraThriftStoreManager.java
	titan-core/src/main/java/com/thinkaurelius/titan/diskstorage/keycolumnvalue/BufferTransaction.java
	titan-core/src/main/java/com/thinkaurelius/titan/diskstorage/keycolumnvalue/StoreTransaction.java
	titan-core/src/main/java/com/thinkaurelius/titan/diskstorage/locking/consistentkey/ExpectedValueCheckingTransaction.java
	titan-persistit/src/main/java/com/thinkaurelius/titan/diskstorage/persistit/PersistitTransaction.java
	titan-test/src/main/java/com/thinkaurelius/titan/diskstorage/inmemory/InMemoryStorageAdapter.java