Rename the version module

The RSpec class is going to have a superclass, but we don't want to
require loading that superclass just to get the version.
Make the reporter stand on its own

We no longer need to have an embedded formatter, which cleans things
up quite a bit. This also means we can simply use multiple formatters
instead of having to specialize our code for each existing formatter.
Rename formatter

This allows us to reclaim the module CI::Reporter::RSpec.
Rename the version module back to the original name
Merge pull request #5 from ci-reporter/standalone-reporter

No longer delegate to a built-in RSpec formatter