Unit testing for def/ module.

Added unit tests to test code in def/ module.

vendor/github.com/mattn/go-isatty/isatty_others.go

@@ -1,9 +1,14 @@
-// +build !windows
-// +build !appengine
+// +build appengine js nacl
 
 package isatty
 
-// IsCygwinTerminal return true if the file descriptor is a cygwin or msys2
+// IsTerminal returns true if the file descriptor is terminal which
+// is always false on js and appengine classic which is a sandboxed PaaS.
+func IsTerminal(fd uintptr) bool {
+	return false
+}
+
+// IsCygwinTerminal() return true if the file descriptor is a cygwin or msys2
 // terminal. This is also always false on this environment.
 func IsCygwinTerminal(fd uintptr) bool {
 	return false