Add ability to follow a user(s) tweets using setFollow()

[brentarcane]

This allows you to follow a one or more users tweets using a whenTweets() method. Under the hood, it's using setFollow() instead of setTrack().

[freekmurze]

To make it clear: $listenFor should be a string or array of twitter handles? If so, rename that variable to $twitterHandles. Could you also update the readme with a good description of the added functionality?

[brentarcane]

$listenFor must be a string or array of Twitter User ID's as per https://dev.twitter.com/streaming/overview/request-parameters#follow

Perhaps $twitterUserIds would be more appropriate?

[freekmurze]

$twitterUserIds sounds good to me 👍

[bradleybernard]

+1 need to filter on user IDs. When will this be merged?

[freekmurze]

Probably in the next couple of days

[freekmurze]

Thank you!