`mix release --erl` is undefined

Steps to reproduce

create a project using Distillery version 2.0.12
run mix release --erl="-sname foo"

Verbose Logs

Paste the output of the release command you ran with the --verbose flag below in the summary tags (this helps keep the issue easy to navigate):

``` $ mix release --erl="-sname foo" --verbose ** (FunctionClauseError) no function clause matching in Mix.Tasks.Release.do_parse_args/2 The following arguments were given to Mix.Tasks.Release.do_parse_args/2: # 1 [erl: "-sname foo", verbose: true] # 2 %{executable: [enabled: false, transient: false], is_upgrade: false, no_tar: false, selected_environment: :default, selected_release: :default, upgrade_from: :latest, verbosity: :normal} Attempted function clauses (showing 10 out of 16): defp do_parse_args([], acc) defp do_parse_args([{:verbose, _} | rest], acc) defp do_parse_args([{:quiet, _} | rest], acc) defp do_parse_args([{:silent, _} | rest], acc) defp do_parse_args([{:profile, profile} | rest], acc) defp do_parse_args([{:name, name} | rest], acc) defp do_parse_args([{:env, name} | rest], acc) defp do_parse_args([{:no_warn_missing, _} | rest], acc) defp do_parse_args([{:no_tar, _} | rest], acc) defp do_parse_args([{:executable, e} | _rest], %{is_upgrade: true}) when e != false lib/distillery/tasks/release.ex:260: Mix.Tasks.Release.do_parse_args/2 lib/distillery/tasks/release.ex:82: Mix.Tasks.Release.run/1 (mix) lib/mix/task.ex:314: Mix.Task.run_task/3 (mix) lib/mix/cli.ex:80: Mix.CLI.run_task/2 (elixir) lib/code.ex:677: Code.require_file/2 ```

Description of issue

What are the expected results? The documented behavior of the --erl flag.
What version of Distillery? 2.0.12
What OS, Erlang/Elixir versions are you seeing this issue on? Mac OS X High Sierra, Elixir 1.6.5, Erlang 20.3.7
If possible, also provide your rel/config.exs, as it is often my first troubleshooting question, and you'll save us both time :) Not the problem this time, the code is missing a function definition.
Is there documentation that says one thing, but Distillery does another? If so, please link the doc here so it can be updated if it's a documentation issue, or so that the fix can be based around what's documented. https://github.com/bitwalker/distillery/blob/master/lib/distillery/tasks/release.ex#L15

bitwalker / distillery