Move OS into RubyFeatures file.

These things belong together, IMO.
Call `module_function` once rather than N times.
Updated travis build scripts (from rspec-dev)
Temporarily add back file that rspec-core  is requiring.
Merge pull request #119 from rspec/merge-ruby-features

Merge ruby features
Merge pull request #121 from rspec/update-travis-build-scripts-2014-10-30-for-master

Updates from rspec-dev (2014-10-30)
Remove file that is no longer needed.

This is a followup to #119 and rspec/rspec-core#1758.
Merge pull request #122 from rspec/remove-unneeded-file

Remove file that is no longer needed.
Add appveyor config file.
Can’t use `super` with no parens inside `define_method`.
On AppVeyor we get permissions errors from mktmpdir.