Merge meta on aliases.

This fixes pass-through-help when used on vector valued aliases. Ex:

    :aliases {"a" ^:pass-through-help ["run" "-m" "some.core"]
              "b" ^:any-meta ["a"]}

The meta on task b will be `{:pass-through-help true, :any-meta true}`.
Merge pull request #1769 from RyanMcG/fix-pass-through-help-on-vector-aliases

Fix pass-through-help on vector aliases by merging meta on aliases