Fix #99

CqlProtocolHandler#on_closed yielded the failed future and not the error
Version bump to v2.0.0.pre2
Remove QueryTrace

It's a remnant of a feature that never became anything. It shouldn't be included.
Update Yard
Mark PeerDiscovery as private
Add API docs for PreparedStatement#batch
Add API docs to PreparedStatement

This closes #104. Also see #93, #102 and #103.
Make QueryResult#next_page return nil on the last page

Also add #last_page? and #next_page to QueryResult so that only that class needs to be public and PageQueryResult can be private.
Add and update the API documentation on paging
Add documentation references
Remove the docs for Client#connect, that method should not be used
Change form a @note to emphasis

@note in Yard is extremely annoying in that it moves to the top.
Remove the documentation for consistency as last argument to #execute

The feature has been deprecated for a while, and it still works, but let's not advertise it.
Update the docs for PreparedStatement#execute with examples and references
Remove the docs for the :host option to Client.connect

It's been deprecated a while, and it will still work, but it doesn't have to be advertised.
Add #last_page? and #next_page to VoidResult
Add class-level documentation to all classes in the Cql::Client namespace
Remove whitespace blank lines
Add docs to VoidResult#last_page? and #next_page
Move authentication support to its own module