title: Installed bower dependencies not on latest commit
body: <p>I have a git project which contains a bower.json file which contains several dependencies.  It looks like this:</p>
  
  <pre><code>//module1
  "dependencies": {
      "devbridge-autocomplete": "devbridge/jQuery-Autocomplete#~1.2.21",
      "backbone": "~1.2.1",
      "underscore": "~1.8.3",
      "jquery": "~2.1.4",
      "module2": "gitUser/module2",
      "module3": "gitUser/module3"
    }
  </code></pre>
  
  <p>problem is when I run <code>bower install --save gitUser/module1</code> bower does not pull the latest commits from github, and only pulls the initial commit.</p>
  
  <p>bower.json of module2 and 3 are essentially similar:</p>
  
  <pre><code>{
    "name": "module2",
    "main": "module2.js",
    "version": "0.0.0",
    "authors": [
      "gitUser &lt;gitUser@gitUser.com&gt;"
    ],
    "moduleType": [
      "amd"
    ],
    "license": "MIT",
    "ignore": [
      "**/.*",
      "node_modules",
      "bower_components",
      "directory/bower_components",
      "test",
      "tests"
    ]
  }
  </code></pre>
  
  <p>the cloned repositories hidden .bower.json looks like:</p>
  
  <pre><code>{
    "name": "module2",
    "_cacheHeaders": {
      "Content-Type": "text/html; charset=utf-8"
    },
    "main": "index",
    "_source": "https://github.com/gitUser/module2",
    "_target": "*",
    "_originalSource": "https://github.com/gitUser/module2"
  }
  </code></pre>
  
  <p>I have also unsuccessfully tried installing dependencies in module1 by:</p>
  
  <pre><code>bower install --save gitUser/module2#latest
  </code></pre>
  
  <p>I have also tried adding git tags to each sub module, but this also did not work.
  I saw <a href="https://github.com/bower/bower/issues/87" rel="nofollow">this</a> issue, so the tagging should not matter.</p>
  
  <p>Any assistance appreciated!</p>