title: Always got undef error of lager_transform when using lager log framework
body: <p>I want to use lager as my log utility and I have orgnazied my proj as below:</p>
  
  <pre><code>proj\
    |
    |--lager\
    |    |--src\
    |    |--ebin\
    |    |--...
    |     
    |--logserver\
    |    |--src\
    |    |--ebin\
    |    |--rebar.config
    |    |--...
    |
    |--rebar
    |
  </code></pre>
  
  <p>However, when I try to compile logserver, I always got the following error:</p>
  
  <p>D:\proj\logserver>..\rebar compile</p>
  
  <pre><code>==&gt; logserver (compile)
  src/logserver_app.erl:none: error in parse transform 'lager_transform': {undef,
                                               [{lager_transform,
                                                 parse_transform,
                                                 [[{attribute,1,file,
                                                    {"src/logserver_app.erl",1}},  
                                                    ...
  </code></pre>
  
  <p>Can anyone know the reason? Thanks!</p>
  
  <p>These is some additional information:</p>
  
  <ul>
  <li>I am using Windows OS and using latest version of Erlang and rebar
  and lager.</li>
  <li>lager itself has already been compiled. We can find the     D:\proj\logserver>dir ..\lager\ebin\lager_transform.beam   (This will
  succeed)</li>
  <li><p>rebar's config file(D:\proj\logserver\rebar.config):</p>
  
  <p>...
    {erl_opts, [{parse_transform, lager_transform}, debug_info,{d,'TEST'}, {i, "include"}, {src_dirs, ["src"]}]}.</p>
  
  <p>{lib_dirs, ["..\lager\ebin"]}.
    ...</p></li>
  </ul>