layout: Make `box-sizing` only affect explicitly-specified or percentage
sizes, not automatically computed ones.

Improves GitHub significantly.
fix debian install instructions
Disable html/semantics/forms/the-input-element/type-change-state.html.ini
auto merge of #3656 : Manishearth/servo/disable-type-change, r=Ms2ger

I haven't yet gotten to the root of this, but it's breaking the other PRs.
auto merge of #3615 : pcwalton/servo/box-sizing-fix, r=glennw

Improves GitHub significantly.

r? @glennw
auto merge of #3627 : steveklabnik/servo/master, r=larsbergstrom

This may be because I'm on Ubuntu, but this was the name of the package.
Create an almost-correct form_owner() for convenience
Add form submission via input element
Add click handler for <input type=submit>
Filter out buttons which aren't the submitter while constructing the dataset
Update wpt expectations