function httpGet (...args) {
	return Observable.create((observer) => {
		needle.get(...args, (error, response) => {
			if (error) observer.error(error)
			else {
				observer.next(response)
				observer.complete()
			}
		})
	})
}
send a GET request to the given HTTP endpoint by passing the supplied
arguments to [`needle`](https://www.npmjs.com/package/needle).
@return {Observable} - observable sequence of a single response object.