Update ANAPIRangeAdapter/NSString+ANAPIRangeAdapter.m

Changed a few things:
- separated the emoji detection to its own method and gave some names to the magic numbers.
- enumerate over the entire string and stop when the adjusted range is passed. since this information is not known a priori you cannot enumerate over anything but the entire string.
- cocoa-ified method names

this is just a swag at this. i haven't done much testing of this proposal outside of my own codebase, but felt like it might help to contribute.