Update README.md

Author: toddlyons

README.md

@@ -1,4 +1,4 @@
 # bfrpg.github.io
-Map of Basic Fantasy RPG Collaborators
+A map of Basic Fantasy RPG Collaborators
 
 If you are a contributor whose name (or forum handle) appears in a publication and you'd like to be on the map, please don't give coordinates to your house. Any pin drop in your city or town will do.