bump jade version

[lunelson]

Updated jade to current version; fixes #114

All tests are passing except the one where it should warn against use of !!! rather than doctype; weird, cause I know there are a bunches of issues there. Maybe it's been undone?

[kennethormandy]

We use a fork of Jade with the patch to warn rather than fail on !!! merged: https://github.com/harp/jade

If you want to open a PR with their upstream changes merged there, we’d accept that. Sadly it looks more complicated this time than just git pull upstream master.

We’re also dropping Node v0.10.x support in the next release, though, so if @sintaxi isn’t bothered either, I think enough time has passed we’d be fine dropping our fork and going back to the main version and dropping !!!.

[lunelson]

Ah, ok I get it, the warning is in your fork. I agree it's going to be too complicated to try to merge the upstream changes; options would be to re-fork the current jade and patch that to warn instead of fail, or as you say just drop the fork and let !!! fail.

Dropping old Node support may be a breaking change for some users anyway so that seems like a reasonable time to do it