Add shim metadata

vic · web-flow · commit 29bb7d19fc17 · 2016-12-14T11:59:22.000-06:00
As per asdf-vm/asdf#122
diff --git a/shims/mix b/shims/mix
@@ -1,3 +1,4 @@
 #!/usr/bin/env elixir
+# asdf-plugin: elixir
 Mix.start
 Mix.CLI.main
