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_default_platform.go

@@ -9,6 +9,7 @@ import (
 func getPlatform() *Platform {
 	return &Platform{
 		os:                   runtime.GOOS,
+		catCmd:               "cat",
 		shell:                "bash",
 		shellArg:             "-c",
 		escapedQuote:         "'",