Minor bug fixes

Updated the licence

Fixed bug when delegate wasn't notified of edited paragraphs or some …

…part of a paragraph if users pasted a string over selected text which has the same length as the inserted string.

Unit tests were updated as well.

Improved paragraph mutation diff to reflect exact paragraph indexes a…

…fter text storage mutation

Changing only attributes of a paragraph (not its characters) now resu…

…lts in editedParagraph change notification of delegate as it should be