Make changes for Elixir v0.13
Fix various errors on 0.13.3.

This is still not passing tests, but should be very close.  It runs at
least.  I believe any remaining issues have to do with my changes to
SessionServer
Fix conflicts and merge branch 'feature/elixir_v0.13_support' of github.com:knewter/hound into knewter-feature/elixir_v0.13_support

Conflicts:
	mix.lock
	test/json_driver/page_test.exs
Bump elixir version and Hound version
Use Enum.map instead of for
Repalces HashDict.merge to HashDict.put
Start phantomjs in port 9090
Down to 4 failing tests
Use Agent instead of custom genserver
Use Agent for ConnectionServer; Use defaults from application env
Bump elixir version; Remove todo
Require Elixir 0.13.0 or greater
Update to work with Elixir 0.14.0
Remove put_in usage for backwards compatibility
Remove instances of get_in for backwards compatibility
Update erlang version for TravisCI to 17.0
Remove inspect line
Move ex_doc to docs env; And update it
Make generic helpers instead of hacking with __using__ to use the right driver module
Delete docs from JSON driver modules