Added asynchronous for loop to show friend's photos

Used this chapter of Mixu's Node.js book
(http://book.mixu.net/node/ch7.html) 7.2.1. (Control flow pattern #1:
Series - an asynchronous for loop) to add a series control flow that
iterates through each item of an array, does something (in this case
gets the friend ID and returns the name and their profile photo), and
once finished *then* calls the view render (profile.ejs). Problems
before this was the asynchronous rendering of the view before the
friends details had arrived, resulting in an empty section where the
profile photos should be. There was also an issue with duplicating
results, but all I had to do was set the array length back to zero
(array.length = 0). Cool, next step is to add the same functionality to
the chat view for profile photos and then decide if MongoDb is the right
choice for a social network (which it probably isn't...).