title: Android Api 24 can't find sources
body: <p>I have this grade file:</p>
  
  <pre><code>//ext.support_library_version = '24.0.0'
  
      android {
          compileSdkVersion 24
          buildToolsVersion '24.0.0'
  
          defaultConfig {
              applicationId "---"
              minSdkVersion 21
              targetSdkVersion 24
              versionCode 1
              versionName "1.0"
          }
      ...
      }
  </code></pre>
  
  <p>But then when i try to open any android related class, it says i haven't got sources for api24, even tho the <code>buildToolsVersion '24.0.0'</code> is installed. Any idea why?</p>