Support of UUID for model attributes is not functional

[jrnt30]

Currently if you have a model that has an attribute of type UUID the generator fails to properly parse and build the model.

Output:

[design/models.go:33] Unsupported type: 0x6 token in unnamed BuildSource
make: *** [generate] Error 1

Example:

var UserType = Type("UserPayload", func() {
	Attribute("id", Integer, "Unique User ID")
	Attribute("real_name", String, "Actual name of user")
	Attribute("user_name", String, "Username of user")
	Attribute("email", String, "Email address of user")
	Attribute("slack_id", String, "Slack ID of user")
	Attribute("token", UUID, "Generated UUID of a user")
})

var UserMedia = MediaType("application/vnd.user+json", func() {
	Reference(UserType)

	Attributes(func() {
		Attribute("id")
		Attribute("real_name")
		Attribute("user_name")
		Attribute("email")
		Attribute("slack_id")
		Attribute("token")
	})

	Required("real_name", "user_name", "email", "slack_id")

	View("default", func() {
		Attribute("id")
		Attribute("real_name")
		Attribute("user_name")
		Attribute("email")
		Attribute("slack_id")
	})
})