title: Error "COMPILE_SDK_VERSION" not found when adding a GPUImage Library to the Project
body: <p>Previously I worked on Eclipse for Android Development, but I have now moved to Android Studio for a specific project and also I wanted to get a hang of Android Studio.</p>
  
  <p>I created a new Project. And then imported a new module to add the library for "GPUImage" from the "Project Explorer". The library got added, but when I compiled the project, I got this </p>
  
  <p>Error : <code>"Error:(4, 0) Could not find property 'COMPILE_SDK_VERSION' on com.android.build.gradle.LibraryExtension_Decorated@171c6271."</code></p>
  
  <p>Tried to follow some tutorials but haven't been able to find any thing. It must be something related to editing the gradle files of the app or library but not sure. Need Help. Thanks!</p>