title: Protobuf issues with imposm.parser on OS X El Capitan
body: <p>I have been trying to install <code>imposm.parser</code> on my MBPro (OSX El Capitan) via <code>pip</code>. I am getting the following error</p>
  
  <pre><code>In file included from imposm/parser/pbf/osm.cc:6:
      imposm/parser/pbf/osm.pb.h:9:10: fatal error: 'google/protobuf/stubs/common.h' file not found
      #include &lt;google/protobuf/stubs/common.h&gt;
           ^
      1 error generated.
      error: command '/usr/bin/clang' failed with exit status 1
  </code></pre>
  
  <p>I already installed protobuf and py2-protobuf using Macports. I also installed Google's Protocol Buffers 2.6.1 from source, but it does not address the issues. Note that the file <code>common.h</code> is actually in the <code>google/protobuf/stubs</code> folder when I checked.</p>