Updated calendar.js

Allow to add custom classes to specific days, thus, now it's possible to
give different colors to specific days as needed.

Example:

		var calendar_default_options = {
			view: 		'month',
			tmpl_path: 	'tmpls/',
			tmpl_cache: false,
			language: 'es-ES', // Spanish
			classes: {
				months: {
					'Fri Feb 07 2014': 'custom-day-class'
				}
			}
		};

		var options = {
			events_source: []
		};

		jQuery.extend ( options, calendar_default_options );
		var calendar = jQuery('#calendar').calendar( options );