*: Add Go 1.14 to test matrix

This also removes Go 1.11 from the test matrix.

Now that 1.14 has been released, as always it should be included in the
test matrix.

.travis.yml

@@ -11,9 +11,9 @@ arch:
 
 go:
   - tip
+  - 1.14.x
   - 1.13.x
   - 1.12.x
-  - 1.11.x
 
 matrix:
   allow_failures: