Add custom layer and page objects with slayer support.
Refactor splinter stuff to keep no references to the browser.

The browser should always be retrievable.
The browser can be easily switched by using @javascript decorator.
Declare missing dependency to splinter.
Use splinter from source.
Splinter zope.testbrowser: let the browser pass the errors.
Plone page object: add some helper methods.
Pages: improve portal message functions.
Move click_button to plone page object, also provide a get_button.
Add dexterity add form support to page objects.
Add plone control panel page object.
Update .gitignore.
Test PageObject.
Start implementing Plone Page Object tests.
Pages: Add optional path argument to Plone.visit_portal.
Pages: Normalize text in Plone.get_first_heading.
Pages: Remove Plone.disable_wysiwyg_for_field: not used anymore.

Use fill_field of the form page object. This handles tinymce.
Pages: Handle tinymce in fill_field for PhantomJS.
Pages: add traceback informations for easier debugging.
Pages: Add Plone page object test.
Pages: add concat_portal_url helper method.