Add contributing and issue template files

.github/CONTRIBUTING.md

@@ -0,0 +1,3 @@
+As questions at [StackOverflow](http://stackoverflow.com/questions/tagged/redigo+go).
+
+Send email to Gary Burd (address in GitHub profile) before doing any work on Redigo.

.github/ISSUE_TEMPLATE.md

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+Please ask questions at http://stackoverflow.com/questions/tagged/redigo+go