OTP 18 support

[jedhu0]

Compiling src/js_benchmark.erl failed:
src/js_benchmark.erl:41: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
src/js_benchmark.erl:43: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
ERROR: compile failed while processing /project_path/erlang_js: rebar_abort
** (Mix) Could not compile dependency :erlang_js, "$HOME/.mix/rebar" command failed. You can recompile this dependency with "mix deps.compile erlang_js", update it with "mix deps.update erlang_js" or clean it with "mix deps.clean erlang_js"

[cmeiklejohn]

See #52.

[jedhu0]

@cmeiklejohn cool !

[pichi]

See #49.

It's simpler and far less invasive.