Use a vendor directory for repeatable builds - fixes #816

This is using godep to manage the vendor directory.

vendor/github.com/inconshreveable/mousetrap/trap_others.go

@@ -0,0 +1,15 @@
+// +build !windows
+
+package mousetrap
+
+// StartedByExplorer returns true if the program was invoked by the user
+// double-clicking on the executable from explorer.exe
+//
+// It is conservative and returns false if any of the internal calls fail.
+// It does not guarantee that the program was run from a terminal. It only can tell you
+// whether it was launched from explorer.exe
+//
+// On non-Windows platforms, it always returns false.
+func StartedByExplorer() bool {
+	return false
+}