Cqlengine

* support for USING TIMESTAMP <microseconds from epoch> via a .timestamp(timedelta(seconds=30)) syntax
- allows for long, timedelta, and datetime
* fixed use of USING TIMESTAMP in batches
* clear TTL and timestamp off models after persisting to DB
* allows UUID without dashes - (Thanks to Michael Hall, github.com/mahall)
* fixes regarding syncing schema settings (thanks Kai Lautaportti github.com/dokai)

* support for execute_on_exception within batches

* fixing create keyspace with network topology strategy
* fixing regression with query expressions

* adding update method
* adding support for ttls
* adding support for per-query consistency
* adding BigInt column (thanks Lifto)
* adding support for timezone aware time uuid functions (thanks dokai)
* only saving collection fields on insert if they've been modified
* adding model method that returns a list of modified columns

* adding support for timeouts

* changing value manager previous value copying to deepcopy