Deprecate page accessor, update dependencies, improve test outcomes.

Functional Changes
===============
* Deprecate the "Page" accessor
* Throw an exception when no browser is set (during parallel runs)
* Take :browser, :version and :os from the relevant variables, or nil them out if unset
* Float the minor version of RSpec.

Dependency Changes
================
* Support parallel_tests 0.15.0
* Update to RSpec 2.13

Testing Changes
============
* Remove gemcutter from a child gemfile
* Added SimpleCov for spec:units