Print a more appropriate message on 'rebar info'

To avoid treating plugins' info/2 functions as commands, we catch calls
to 'rebar info'. Previously (4b8c81fb) we simply printed the help
string, but it's much more informative to print the following:
Command 'info' not understood or not applicable

src/rebar.erl

@@ -87,7 +87,9 @@ run(["help"|RawCmds]) when RawCmds =/= [] ->
 run(["help"]) ->
     help();
 run(["info"|_]) ->
-    help();
+    %% Catch calls to 'rebar info' to avoid treating plugins' info/2 functions
+    %% as commands.
+    ?CONSOLE("Command 'info' not understood or not applicable~n", []);
 run(["version"]) ->
     ok = load_rebar_app(),
     %% Display vsn and build time info