build.gradle has been configured as per github insturctions.LeakCanary class doesn't seem to be included.
dependencies {
debugCompile 'com.squareup.leakcanary:leakcanary-android:1.3'
releaseCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.3'
}
analyzer and watcher packages has just 1 single class file in it.
Rebuilding the project fixed it for me.
There's a deleted answer (I don't know why) by Kaushik Gopal that gives this solution and points to a Github issue