disabling auto snapshoting functionality by default

IMHO, snapshoting is not that useful for unit testing, as it just
increases test runtime.  Additionally, disabling auto snapshoting will
remove the dreaded "mklink: Path too long" error
added additional constructors to AbstractCassandraUnit4TestCase

These constructors simply pass the args to CassandraUnit so that you can
specify the configurationFile and host you wanna use when you subclass
AbstractCassandraUnit4TestCase.  This allows for the same functionality
whether you're using the CassandraUnit with @Rule or subclassing
AbstractCassandraUnit4TestCase