Add README for bolts module (#1045)

* Add README for bolts module

* Update README.md

Author: Jawnnypoo

bolts-tasks/README.md

@@ -0,0 +1,4 @@
+## bolts-tasks
+Fork of [Bolts-Android](https://github.com/BoltsFramework/Bolts-Android), since it is no longer
+really maintained/supported. Moving it here gives us the control over the dependency and allow us to shift
+to other async solutions, such as Kotlin coroutines, long-term.