fix #1232 Check tpl context still exists on widget

Just check that the associated template context for a widget still exists
before trying to execute a given callback on it.

Fixes #1232
Close #1233
fix #1226 Changing cursor for disabled list widget

Chaging the cursor from pointer to default for disabled items inside a list widget
fix #1236 The alpha international validator accepted numbers
feat #1231 Highlighting the selected options in selectbox widget

This commit makes the selected option highlighted when clicked on dropdown
of selectbox widget
close #1231
fix #1021 getElementsByClassName discrepancy in Fx 3.6

Modern browsers, and IE7+ coerce the class parameter to a string
automatically, it was not the case in Firefox 3.6.

Close #1246.
1.6.3
fix #1249 Updating type check for Array

The check for array was not working properly, this commit change the condition in order to use the aria.utils.Type.isArray method instead.
feat #1235 Add grunt tasks to ease packaging

This commit introduces
- a grunt multi-task (`atbuild`) that allows to simply re-package aria templates source code. It is also used internally for the production build of the framework.
- a grunt multi-task (`easypackage`) that allows to create packages for an aria templates-based application. It simplifies the configuration that is generally needed in order to achieve this goal by exposing a simple API to the developer.

These tasks are now available in any project including the framework. The necessary files are published to npm along with the framework and there is no need to explicitly add atpackager or noder-js as dependencies in order to execute them.

Close #1235