Bring annotation view to front when selected

[1ec5]

Fixes #991. Split out from #5245.

/cc @boundsj

[1ec5]

The Android build is failing due to something completely unrelated to this PR, maybe out of our control too:

* What went wrong:
A problem occurred configuring project ':MapboxGLAndroidSDKTestApp'.
> Could not resolve all dependencies for configuration ':MapboxGLAndroidSDKTestApp:_debugCompile'.
   > Could not determine artifacts for com.squareup.leakcanary:leakcanary-android:1.4-beta1
      > Could not get resource 'https://jcenter.bintray.com/com/squareup/leakcanary/leakcanary-android/1.4-beta1/leakcanary-android-1.4-beta1.aar'.
         > Could not HEAD 'https://jcenter.bintray.com/com/squareup/leakcanary/leakcanary-android/1.4-beta1/leakcanary-android-1.4-beta1.aar'. Received status code 500 from server: Internal Server Error