Amended "if data" checks in FileModel to "if data?"

Signed-off-by: Richard Antecki <richard@antecki.id.au>
Merge branch 'master' into rantecki-20130310
Merge pull request #454 from rantecki/rantecki-20130310

"if data" checks in FileModel
Merge branch 'master' into dev
v6.30.2. Bugfix. Improvement.

- v6.30.2 April 7, 2013
	- Allow for empty `data` when injecting files into the database
		- Thanks to [Richard A](https://github.com/rantecki) for [pull
request #454](https://github.com/bevry/docpad/pull/454)
	- Fixed "No Skeleton" option not working (bug introduced in v6.30.0)
		- Thanks to [Adrian Olaru](https://github.com/adrianolaru) for [pull
request #475](https://github.com/bevry/docpad/issues/475)