Return meaningful error values when parsing#155

Merged

bors-servo merged 3 commits intoservo:masterfrom

Jun 9, 2017

Commits on Jun 7, 2017

Return more specific parse error data.
jdm
committed

Commits on Jun 8, 2017

Make parse error types extensible.
jdm
committed

Commits on Jun 9, 2017

Make Parser always borrow its input.
jdm
committed