Erlang release for Elixir should use start.boot instead of elixir.boot
Continue checking first for a mixfile before a rebarconfig
Check the key on register_attribute
Allow -boot start to be overriden on releases
Raise an error when Dict/Set doesn't support the target
Merge pull request #1403 from devinus/raise-on-unsupported-dictset

Raise an error when Dict/Set doesn't support the target