Support dialyzer plt paths having "~/" as a prefix

e.g. {dialyzer_opts, [{plt, "~/.dialyzer_plt.R14B"}]}.

src/rebar_dialyzer.erl

@@ -193,6 +193,8 @@ existing_plt_path(Config, File) ->
                             ?ABORT("No PLT found~n", [])
                     end
             end;
+        [$~|[$/|Plt]] ->
+            filename:join(Home,Plt);
         Plt ->
             Plt
     end.