title: add a sub podspec for a dependency framework to existing podspec
body: <p>My pod spec has some dependencies , but i need to add another podspec which is hosted on local folder but it point to server is that possible?</p>
  <p>s.source has only 1 git and commit id, is it possible to add another ?</p>
  <p>s.dependency 'framework', :podspec:=&gt; ''
  returns error</p>
  <pre><code>file: [!] Unsupported version requirements. [{:podspec=&gt;&quot;
  </code></pre>