Switch to ginkgo/gomega for tests

This switches over to ginkgo/gomega for tests, which makes writing
certain tests easier/more fluent in the future.

vendor/github.com/onsi/gomega/matchers/not.go

@@ -0,0 +1,30 @@
+package matchers
+
+import (
+	"github.com/onsi/gomega/internal/oraclematcher"
+	"github.com/onsi/gomega/types"
+)
+
+type NotMatcher struct {
+	Matcher types.GomegaMatcher
+}
+
+func (m *NotMatcher) Match(actual interface{}) (bool, error) {
+	success, err := m.Matcher.Match(actual)
+	if err != nil {
+		return false, err
+	}
+	return !success, nil
+}
+
+func (m *NotMatcher) FailureMessage(actual interface{}) (message string) {
+	return m.Matcher.NegatedFailureMessage(actual) // works beautifully
+}
+
+func (m *NotMatcher) NegatedFailureMessage(actual interface{}) (message string) {
+	return m.Matcher.FailureMessage(actual) // works beautifully
+}
+
+func (m *NotMatcher) MatchMayChangeInTheFuture(actual interface{}) bool {
+	return oraclematcher.MatchMayChangeInTheFuture(m.Matcher, actual) // just return m.Matcher's value
+}