Basic RSpec support


Basic RSpec support

Implemented basic RSpec integration.

A MediawikiSelenium::Environment instance is created before each
example and exposed as a mw method. It looks for and loads an
environments.yml configuration in the current working directory.

Indirect/unqualified calls on mw methods (e.g. just on_wiki instead
of mw.on_wiki) are also allowed via dynamic dispatch.

All helpers except for StrictPending (which is Cucumber specific) are

See features/rspec.feature for what an RSpec based integration test
could look like.

Bug: T108273
Change-Id: I97a7522764fd535ef8f3510fd654df8976d70af0