Updated travis build scripts (from rspec-dev)
`[.]` doesn’t appear to work well on windows.
Pend symlink specs on windows.
Fix ansicon specs on windows.

- Explicitly clear `ANSICON` ENV var in the context
  concerning when it’s not set. On appveyor we
  install ANSICON so it is in fact normally set.
- Move the specs out of the context that sets
  `config.color = true` in a `before` hook. This
  was causing problems because it triggered warnings
  before our `allow_warnings` code had a chance to
  silence them.
Fix rake task specs on windows.

- Skip specs that rely on shell escaping (not available on windows).
- On windows we wrap all args in single quotes, so change our
  expectations to allow for that.
Use platform-agnostic constant for file path separator.

This should (hopefully) fix the rake task specs on windows.
Skip a couple of specs on windows that don’t make sense to run there.
Pend remaining failing appveyor specs.
Merge pull request #1780 from rspec/update-travis-build-scripts-2014-11-13-for-master

Updates from rspec-dev (2014-11-13)