Adding test for CSS regions support

[mibalan]

Fix for #528, based on parsing of the flow-into property only. Implemented as an add-on.

[matthewrobertson]

For now, the behaviour based check is the only way this is going to work in chrome canary. Please see my comment in #528

[addyosmani]

Given the behaviour based check is the only way this can work until CSS regions are considered stable, I would say this is good to go.

[mibalan]

OK, so this should be it - behavior-based, slimmer, more reliable and with a lot more comments :)

As far as I know, IE10 currently only allows use of CSS Regions on iframe-s, but that's not included in my code (mainly because it's very likely IE will update to a more spec-compliant behavior (since they're co-authoring it, too) ).

[mibalan]

@schmidsi thanks a lot for the tip. It seems that my approach generated invalid flow names, hence the false negative. I fixed the code, settling for a fixed, hardcoded, unlikely to be duplicated flow name :)

[paulirish]

pulling! thanks for this very fine work!