Change scripts block to allow custom attributes
v6.21.4. Bugfix. Improvement.

- v6.21.4 January 16, 2013
	- Fixed incorrect meta data parsing for certain files
		- Closes [issue #394](https://github.com/bevry/docpad/issues/394)
thanks to [Jose Quesada](https://github.com/quesada) and
[Stefan](https://github.com/stegrams)
	- Scripts and styles blocks now support an `attrs` option string
		- Closes [pull request
#397](https://github.com/bevry/docpad/pull/397) thanks to
[Alex](https://github.com/amesarosh)
		- Closes [issue #400](https://github.com/bevry/docpad/issues/400)
thanks to [edzillion](https://github.com/edzillion)