Bump doctest upper bound to 0.17

Porges · web-flow · commit 2670854a238c · 2018-07-03T11:32:07.000+10:00
Addressing commercialhaskell/stackage#3763
diff --git a/email-validate.cabal b/email-validate.cabal
@@ -56,5 +56,5 @@ test-suite doctests
     main-is: doctests.hs
     build-depends:
         base >= 4 && < 5,
-        doctest >= 0.8 && < 0.16
+        doctest >= 0.8 && < 0.17
 
