Make proper and neotoma dev-only dependencies

This patch makes erlware_commons easier to include as a dependency by
removing depedencies that are not needed at run time.

The top-level Makefile creates a .DEV_MODE marker file which is
detected by rebar.config.script. When the marker file is present, the
development only dependencies proper and neotoma are included and a
macro 'DEV_ONLY' is defined. The macro is used to only enable the
proper tests for development mode.

The ec_semver_parser.peg is now located in priv/ and is moved into
src/ by the Makefile. The generated ec_semver_parser.erl is now under
version control; it need not be rebuilt by all projects wishing to
include erlware_commons. It will be rebuilt, as before this change, on
every make invocation.

rebar.config.script

@@ -1,15 +1,42 @@
+%% Merge the list values in `ToAdd' into the list found at key `Key'
+%% in proplist `C'. Don't duplicate items. New Items are added to the
+%% front of existing items. It is an error if the value at `Key' is
+%% not a list in `C'.
+MergeConfig = fun({Key, ToAdd}, C) ->
+                      case lists:keyfind(Key, 1, C) of
+                          false ->
+                              lists:keystore(Key, 1, C, {Key, ToAdd});
+                          {Key, List} when is_list(List) ->
+                              %% remove items in ToAdd already in List
+                              ToAdd1 = [ I || I <- ToAdd, not lists:member(I, List) ],
+                              lists:keystore(Key, 1, C, {Key, ToAdd1 ++ List })
+                      end
+              end.
+
 {match, [ErtsNumber]} = re:run(erlang:system_info(otp_release), "R(\\d+).+", [{capture, [1], list}]),
 ErtsVsn = erlang:list_to_integer(ErtsNumber),
-Opts1 = case lists:keysearch(erl_opts, 1, CONFIG) of
-            {value, {erl_opts, Opts0}} ->
-                Opts0;
-            false ->
-                []
-        end,
-Opts2 = if
-            ErtsVsn >= 15 ->
-                [{d, have_callback_support} | Opts1];	
-             true ->
-                Opts1
-        end,
-lists:keystore(erl_opts, 1, CONFIG, {erl_opts, Opts2}).
+AddErlOpts = if
+                 ErtsVsn >= 15 ->
+                     [{d, have_callback_support}];
+                 true ->
+                     []
+             end,
+
+DevOnlyDeps = [{neotoma, "",
+                {git, "https://github.com/seancribbs/neotoma.git", {branch, master}}},
+               {proper, "",
+                {git, "https://github.com/bkearns/proper.git", {branch, master}}}],
+
+Config1 = MergeConfig({erl_opts, AddErlOpts}, CONFIG),
+
+ConfigPath = filename:dirname(SCRIPT),
+DevMarker = filename:join([ConfigPath, ".DEV_MODE"]),
+case filelib:is_file(DevMarker) of
+    true ->
+        lists:foldl(MergeConfig, Config1,
+                    [{deps, DevOnlyDeps},
+                     {erl_opts, [{d, 'DEV_ONLY'}]}]);
+    false ->
+        Config1
+end.
+