Use hiddenTextArea to generate inputs for IText - POC

Change-Id: I67e51cb1d4720f2c3df27d01c2fd9531681dc908
Merge branch 'master' of github.com:vamo89/fabric.js

Conflicts:
	src/mixins/itext_key_behavior.mixin.js

Change-Id: I57b58111d2ce58b9c2a910a95d36ff7822e63da5