Added: Caching for prepared statements and prepare action

Prepared statements are added to a cache to prevent repeated preparation.  Also
adds a new action, prepare, to allow all prepared statements to be prepared
when starting the module.
Merge pull request #3 from andyjduncan/master

Added: Caching for prepared statements and prepare action
Changed: Updated Vert.x and Cassandra Driver version
Added: Prepared Statement Cache with size limit

Changed: Vert.x maven plugin (2.0.7 -> 2.0.8)
Changed: Minor testComplete (finally) alignment
Changed: Readme explanation for 0.3.5
Fixed: Misspelled @param
Changed: Prepared statement cache size must be at least 1