Move firefox plugin out of main app.
Task to fetch webdriver.xpi
Fix missing file message
Clean up file check logic
Add missing do
Bump version
Bump Version
Merge pull request #28 from stuart/feature/load_firefox_plugin_task

Feature/load firefox plugin task
Raise a better error if an invalid element is passed to the commands
Better handling of unfound elements
Merge branch 'feature/nil_element_response' of github.com:stuart/elixir-webdriver into feature/nil_element_response

Conflicts:
	lib/webdriver/element.ex
	test/webdriver/chrome_session_test.exs
	test/webdriver/firefox_session_test.exs
	test/webdriver/phantomjs_session_test.exs