makeurl functionality now uses http_build_query

**As requested by Arjan Haverkamp:**

I am using a redirect-uri with a question mark in it, something like this: http://mysite.com/auth/foursquare/?authDone=1.

When I use this redirect_uri with your class, Foursquare keeps complaining about a "redirect_uri_mismatch". It took me quite some time to figure out where the problem was, but I did eventually manage to find it.

Your 'MakeURL' function is not properly url-encoding the question mark in the redirect-uri.