Error handling. Vendoring

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

vendor/gopkg.in/dixonwille/wlog.v2/interface.go

@@ -0,0 +1,14 @@
+package wlog
+
+// UI simply writes to an io.Writer with a new line appended to each call.
+// It also has the ability to ask a question and return a response.
+type UI interface {
+	Log(string)
+	Output(string)
+	Success(string)
+	Info(string)
+	Error(string)
+	Warn(string)
+	Running(string)
+	Ask(string, string) (string, error)
+}