Adds some package docs (#479)

Was just browing godoc and noticed we are missing some docs that would
be quite useful.

manager/doc.go

@@ -0,0 +1,7 @@
+// Package manager provides access to kubernetes resources for providers.
+//
+// DEPRECATION WARNING:
+// Though this package is still in use, it should be considered deprecated as it
+// is just wrapping a k8s client and not much else.
+// Implementers should look at replacing their use of this with something else.
+package manager