`[.]` 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.