Make rebar3_efmt a project plugin

rebar.config

@@ -26,8 +26,6 @@
 {profiles, [{native, [{erl_opts, [{d, 'ENABLE_HIPE'}]}]},
             {edown, [{edoc_opts, [{doclet, edown_doclet}]}, {deps, [edown]}]}]}.
 
-{project_plugins, [covertool]}.
+{project_plugins, [covertool, rebar3_efmt]}.
 {cover_export_enabled, true}.
 {covertool, [{coverdata_files, ["ct.coverdata", "eunit.coverdata"]}]}.
-
-{plugins, [rebar3_efmt]}.