Jan Hudzik

Added whole .idea directories to the .gitignore as none of their content is currently tracked

Updated Android plugin for Gradle and removed android.buildToolsVersion parameter as it is optional from now on. https://androidstudio.googleblog.com/2017/10/android-studio-30-beta-7-is-now.html The same changeset as in https://github.com/googlecodelabs/android-backup-codelab/pull/1, just with correct user email set