Remove rebar3 elvis plugin reference, close #118 (#119)

Author: deadtrickster

rebar.config

@@ -45,8 +45,7 @@
                         "https://github.com/deadtrickster/prometheus.erl"}}]}]},
             {test, [
                     {eunit_compile_opts, [{src_dirs, ["src", "test/eunit"]}]},
-                    {plugins, [{coveralls, "1.4.0"},
-                               {rebar3_elvis_plugin, "0.0.4"}]}]},
+                    {plugins, [{coveralls, "1.4.0"}]}]},
             {gpb, [{plugins, [{rebar3_gpb_plugin, "2.7.0"}]},
                    {provider_hooks, [{pre,  [{compile, {protobuf, compile}}]},
                                      {post, [{clean,   {protobuf, clean}}]}]},