Remove unused imports.
auto merge of #1481 : Ms2ger/servo/unused-imports-2, r=metajack
add names for all servo spawned tasks

* add servo_util::task::{spawn_named,spawn_with_named} functions

* add name param for spawn_listener and spawn_conversation functions

this should resolve #1169
Enable checks for reftest exit status.
auto merge of #1484 : metajack/servo/check-reftest-status, r=larsbergstrom

r? @larsbergstrom
auto merge of #1457 : zmike/servo/master, r=jdm

this should resolve #1169