Made more readable printout of the erlydtl compiler message

The printed message is made more terse.

Example before applying patch:

    ERROR: Compiling template src/view/test.dtl failed:
      {error,{"src/view/test.dtl",
              [{{4,7},
                erlydtl_parser,
                ["syntax error before: ",["\"\\\"HELLO_WORLD\\\"\""]]}]}}

Example after applying patch:

    ERROR: Compiling template "src/cmp_html_error_template.dtl" failed:
        (line:3, col:12): ["syntax error before: ",["trans"]]

src/rebar_erlydtl_compiler.erl

@@ -190,12 +190,18 @@ do_compile(Source, Target, DtlOpts) ->
                          module_name(Target),
                          Opts) of
         ok -> ok;
+        {error, {File, [{Pos, _Mod, Err}]}} ->
+            ?ERROR("Compiling template ~p failed:~n    (~s): ~p~n",
+                [File, err_location(Pos), Err]);
         Reason ->
             ?ERROR("Compiling template ~s failed:~n  ~p~n",
                    [Source, Reason]),
             ?FAIL
     end.
 
+err_location({L,C}) -> io_lib:format("line:~w, col:~w", [L, C]);
+err_location(L)     -> io_lib:format("line:~w", [L]).
+
 module_name(Target) ->
     F = filename:basename(Target),
     string:substr(F, 1, length(F)-length(".beam")).