Image size is not correctly handled in DTRichTextEditor

[ftkghost]

Repro steps:

1. Copy rich text content from a web page with text and image (image should be wider than DTRichTextEditor width).
2. Paste it to DTRichTextEditor (Parse the copied "Apple Web Archive pasteboard type" with DTWebArchieve, then create NSAttributeString with DTWebArchieve).

Expected:
The image should fit in DTRichTextEditor

Actual:
The image is not property resized, part of the image is cut by DTRichTextEditor bounds.