Remove the info on C* 2.0 not yet being supported

[ci skip]
Belatedly rename connection_sequence_spec.rb connector_spec.rb
Use different CQL versions for different versions of the protocol

And make it possible to override the version with the :cql_version option
Change the API docs links to use the GitHub not gems version

The gems version includes all of the private APIs

[ci skip]
Include .yardopts in the gem to make rubydoc.info not show private APIs
Remove know limitation that v2 features are not supported

[ci skip]
Update performance tips with the new batching feature

[ci skip]
Add an example of how to enable logging to the readme

Closes #70

[ci skip]