Adding support for 'fraction' resource type

This fixes issue #1103

Change-Id: I8ef799d91d3f99e5b45d05de9a20af8b09e54825
Merge pull request #1104 from spotify/add_fraction_resource_type

Adding support for 'fraction' resource type
Fix flaky test
Add ticker and contentInfo to ShadowNotification.

Closes #1108.
Handle null strings in ShadowNotification.Builder.

This fixes an NPE when using NotificationCompat.Builder from the
support library, since it will call builder methods with null input.