Ignore spec binstubs.
Remove unused :limit and :suffix options from Array#to_list.
Remove DepTemplate options -- they're never used for anything.
Deprecate meta options in the DSL.

The :for option is occasionally passed in because I mistakenly used it
in the README. It never actually did anything.
Extract cleanup logic from Asset#process_extract.
Refactor & spec BrewHelper#active_version_of and #versions_of.
Extract brew parsing logic out into #version_info_for.

This lets us decouple the stubs in the specs too.
Parse `gem env` output as yaml instead of using #val_for.
Remove deprecated methods from GemHelper (deprecated 8 months ago).
Merge branch 'cleanups'