added support for connection pool size allowing multiple connections per host
added support for connection pool size allowing multiple connections per host

ably-forks/nodejs-driver,datastax/nodejs-driver,Teino1978-Corp/nodejs-driver,datastax/nodejs-driver,thiagoveras/nodejs-driver,chrisjsimpson/nodejs-driver,jorgebay/nodejs-driver,connor4312/nodejs-driver,Applifier/node-cassandra-cql,jonathanleang/nodejs-driver,jorgebay/node-cassandra-cql,Applifier/nodejs-driver,layerhq/nodejs-driver