Doesn't work with Grav 1.4.5

[lufik]

The hook onTwigSiteVariables is fired after Twig template ( getgrav/grav#1163 ).

It's enough to change the name of the hook to onTwigPageVariables and everything works like a charm:

		$this->enable([
//			'onTwigSiteVariables' => ['onTwigSiteVariables', 0]
			'onTwigPageVariables' => ['onTwigSiteVariables', 0]
		]);