The reason for deprecating loops is two fold:
1) It reduces the number of special forms. Special forms usually
allow a variable number of arguments and have special scoping
rules and they cannot be overridden or removed;
2) Anonymous looping is highly uncommon in Erlang and slower
than if we loop using named functions;
loop may be added back in the future as a non special form.
rebar expects its dependencies to have a file at `src/elixir.app.src`.
This is a work around a rebar limitation since it should support a way
to have an umbrella application, as OTP.
José Valim