title: How to change the build tools version number for all of my modules in Android Studio/Gradle?
body: <p>I downloaded the new build tools in Android Studio (21.0.1 as of Oct 21, 2014). I then deleted 20.0.0 that I had in SDK Manager. Then building in Android Studio failed saying it couldn't find 20.0.0. I thought I had deleted it. I then found it being referenced in my app module in build.gradle. I changed it, and then I built again, but it failed. I found a reference in the rest of my modules (4 of them to be exact). Any idea how to change the build tool version numbers everywhere? Can I just delete the build tools version number in all of my modules except my app module? It's my first time upgrading build tools while having Android Studio so I wanna make sure I don't mess anything up.</p>