fix issue #640 add catCmd and OS-specific values

Add a catCmd to the Platform struct and set the value to "cat" for
non-windows builds and "type" for windows builds.

pkg/commands/os.go

@@ -23,6 +23,7 @@ import (
 // Platform stores the os state
 type Platform struct {
 	os                   string
+	catCmd               string
 	shell                string
 	shellArg             string
 	escapedQuote         string