Update for easing function names regexp

A tiny update that fixes the bug when trying to apply easing function on attribute animation. Current regexp works fine when you use something like "left[outCubic]: 50px" but fails on "@data-num[outCubic]: 100".
Nope, this wouldn't work. When you run this regexp on a string like <code>@data-animate[easing]: 100</code> the result would be:
<code>["@data-animate[easing]", "<strong>data-animate</strong>", "easing"]</code>
Instead of: 
<code>["@data-animate[easing]", "<strong>@data-animate</strong>", "easing"]</code>

And the <code>@</code> is required there because you use it then as a name of a property to animate. And you need it to check if it's an attribute or a style.

Although, it could be <code>/^(@?[a-z\-]+)\[(\w+)\]$/</code>. But the result is quite the same.