Add "check" alias for testing

Follows GNU Coding Standards, see
https://www.gnu.org/prep/standards/html_node/Standard-Targets.html#Standard-Targets

Makefile

@@ -62,6 +62,9 @@ lint:
 test:
 	for PKG in $(PACKAGES); do go test -cover -coverprofile $$GOPATH/src/$$PKG/coverage.out $$PKG || exit 1; done;
 
+# As for GNU Coding Standard
+check: test
+
 .PHONY: install
 install: $(BIN)/$(EXECUTABLE)
 	cp $< $(GOPATH)/bin/