Search for abbreviation in editor from current caret position
@param {IEmmetEditor} editor Editor instance
@return {String}
function(editor) {
			/** @type Range */
			var range = require('range').create(editor.getSelectionRange());
			var content = String(editor.getContent());
			if (range.length()) {
				// abbreviation is selected by user
				return range.substring(content);
			}
			
			// search for new abbreviation from current caret position
			var curLine = editor.getCurrentLineRange();
			return require('actionUtils').extractAbbreviation(content.substring(curLine.start, range.start));
		}