Error when using POST and postFields is mult-dimensional array.

[zgott]

Great library over all.

I tried to comment on your stackoverflow answer but don't have a high enough reputation.

I'm running into issues trying to make requests similar to the ones on this Twitter API Doc Page. You'll see that the example post body is multi-dimensionl. This throws the error:

Warning: rawurlencode() expects parameter 1 to be string, array given in TwitterAPIExchange.php on line 345

[plamworapot]

Marge requested #250