Poll Cassandra Embedded server during tests to see when ready rather than sleeping
Fix bugs with readColumnSlice related to "reverse" when using Datastax driver

	- When "reverse" flag is passed it also reverses the meaning of start and end
	- Datastax can't order by column without mixing up the keys as well.
		Handle reverse internally rather than relying on Cassandra to do it.
Merge pull request #21 from dennisdurkin/master

Poll Cassandra Embedded server during tests to see when ready