Made the `cqerl:new_client/2` work with default connection infos

As the README says, it is supposed to work with a first argument set to `{}`
Merge branch 'master' of github.com:matehat/cqerl
Made cqerl:new_client return `{ok, Client}`
Removed warnings from cqerl_client
Fixed bug with incorrect timeout value

... when handling sleep time
Fixed an issue with client allocation

Fix #1
When the client has a `keyspace` option set, send that to C* before switching to live state
Ensure the random client selection test does not specify a keyspace

... as it is not yet existent on C* side
Update README.md
Fixed handling of null values