[chore] Drop Go 1.7 x Gin (latest) unit test combo (#118)

[chore] Drop Go 1.7 x Gin (latest) unit test combo

.travis.yml

@@ -12,6 +12,7 @@ addons:
 jobs:
   include:
     - stage: gotest
+      env: GO_VERSION=1.7
       script: make ci
       go: "1.7"
     - script: make ci

Makefile

@@ -12,9 +12,14 @@ updatedeps:
 	go get -v -d -u ./...
 
 test: alldeps
-	#TODO: 2018-09-20 Not testing the 'errors' package as it relies on some very runtime-specific implementation details.
-	# The testing of 'errors' needs to be revisited
-	go test . ./gin ./martini ./negroni ./sessions ./headers
+	@#TODO: 2018-09-20 Not testing the 'errors' package as it relies on some very runtime-specific implementation details.
+	@# The testing of 'errors' needs to be revisited
+	@# Additionally skipping Gin if the Go version is 1.7, as the latest version of Gin has dropped support.
+	@if [ "$(GO_VERSION)" = "1.7" ]; then \
+		go test . ./martini ./negroni ./sessions ./headers; \
+	else \
+		go test . ./gin ./martini ./negroni ./sessions ./headers; \
+	fi
 	@go vet 2>/dev/null ; if [ $$? -eq 3 ]; then \
 		go get golang.org/x/tools/cmd/vet; \
 	fi