Update .travis.yml

Go 1.10 introduced the new strings.Builder type used in the typed error response PR, so v2.0.0 onward must start it's minimum version support at 1.10.

Author: ZachtimusPrime

.travis.yml

@@ -1,9 +1,14 @@
 language: go
 go:
-        - 1.5.x
-        - 1.6.x
-        - 1.7.x
+#         - 1.5.x
+#         - 1.6.x
+#         - 1.7.x
         - 1.10.x
+        - 1.11.x
+        - 1.12.x
+        - 1.13.x
+        - 1.14.x
+        - 1.15.x
 before_install:
         # - go get github.com/mattn/goveralls   # code coverage tracking
         - go get -t -v ./...                  # grab project dependencies (non-vendor)