Reorganized the class hierary in com.swoop.data.mongo

* MongoCollectionConnector now has 2 subclassed versions for
  cacheable queries: memcached based and guava based.
* Using com.amazonaws.elasticache-java-cluster-client for the
  memcached client so that it could work with elasticache
  cache clusters, and autodiscovery.
* Introduced DatastoreStats interface so that cache statistics
  could be exposed.
Refactored .travis.yml a little
Added MemcachedMongoCollectionConnector#getClient to retrieve memcache client
Added some documentation for CacheSettings
Adding in cache invalidation logic
Added aggregate stat calculation for MemcachedMongoCollectionConnector
Inserting calculated stats as numbers instead of strings
Made constructor of FindListCommand public to allow for easy creation of commands with projections.
Updated .travis.yml to use Swoop's maven mirror
Inheriting Swoop's organization POM
Updated .travis.yml to list Swoop public-release repo
Updated swoop-pom to 1.4
Resolved deprecation notices in json-validator-mojo