Sanitize CQL Statements

Thanks for starting this project!  I have tried them all, and cql-rb and cql_model is the winning combination when starting new projects on Cassandra 1.2.

This pull request fixes a handful of issues, most notably ensuring the attribute values are being properly sanitized and escaped on the way into Cassandra.  This allows UUID types (and presumably all other standard types) to now save properly.  It adds a new Cql::Statement class which is a port of CassandraCQL::Statement to parameterize the CQL statements.