yampa: Add period to end of haddock messages for consistency (KSG Has…

…kell 1.3.0 - 5.5). Refs #266.

Prefer consistent names, structure, and improvements over localized
optimizations. For example, a module might define an API in a particular
order, and a module with a similar but distinct API might list elements
in a completely different order. Whenever possible, code should be
consistent.

yampa/src/FRP/Yampa/Diagnostics.hs

@@ -10,7 +10,7 @@
 -- Stability   : provisional
 -- Portability : portable
 --
--- Standardized error-reporting for Yampa
+-- Standardized error-reporting for Yampa.
 module FRP.Yampa.Diagnostics
     ( usrErr
     , intErr