Fix SupervisorTest :push handle_cast method

* handle_cast/2 does not take 'from' param
Merge pull request #2878 from akira/supervisor_test_fix

Fix SupervisorTest :push handle_cast method
Move 0 index match to the function head in `String.split_at/2`
Move same pos match to the function head in `Regex.apply_list/5`
Merge pull request #2879 from lexmag/move-to-fun-heads

Move guards to fun heads
Merge branch 'master' of https://github.com/elixir-lang/elixir