TLSwipeForOptionsCell's buttons are now customizable

Added this to TLSwipeForOptionsCell
```obj-c
- (void)addButtonWithOptions:(NSDictionary *)options;
```

Removed hardcoded TLSwipeForOptionsCellDelegate functions and added this one instead;
```obj-c
- (void)cell:(TLSwipeForOptionsCell *)cell didSelectButtonAtIndex:(NSUInteger)index withInfoDictionary:(NSDictionary *)info;
```
Would it be better to use `self.objects` instead of referring to the ivar directly?