1) cache the scale in the font adjuster. The adjuster will be dealloc'ed when the renderer that owns it is dealloc'ed (or invalidated). Until that time we can trust the scale that the adjuster has computed.
2) When measuring line count, make sure that we are not bounding the height of the container's size. This will cause the wrong number of lines to be returned.
3) Instead of setting the ascender/descender on an ASTextNode when an attributed string is added, wait until after the renderer calculates size. This way, if there is any need to scale the font to fit we can apply that scale to the ascender/descender.
Was running into issues where the scale factor would get cleared when setting a new atributedString on a textNode.
I was clearing out the currentScaleFactor when setting an attributedString into a textNode. It appears that `_calculateSize` isn't always called when setting a new string into a ASTextNode. It can be the case that only `drawInContext:bounds:` is called. With _currentScaleFactor cleared out the renderer that calls`drawInContext...` was being called with a scaleFactor of 0.
It could be the case that the fix could be to remove the clearing of `currentScaleFactor` from `setAttributedString`, but this seems like a safer fix to me. It does, however, require an extra run through the font adjuster when enabled.
* Added a member to `ASTextKitAttributes` that is an optional delegate to the struct's NSLayoutManager.
* Changed ASTextNode to set this delegate to an instance of ASTextNodeWordKerner.
* Updated init method of `ASTextKitContext` to take an optional NSLayoutManager delegate
* Added the files in TextKit folder to the public headers (so we can include ASTextNodeTypes.h)
