Add option to set an exact UIFont

[revolter]

I find it out a no-brainer to be able to directly set a UIFont instead of a name and size. In most cases I already have a UIFont instance, and currently I have to use:

UIFont *myFont = ...;
@"Test text".typeset.font(myFont.fontName, myFont.pointSize);

instead of:

UIFont *myFont = ...;
@"Test text".typeset.exactFont(myFont);

The only thing I'm not very fond of is the exactFont name. :/