Use downloaded snapshots instead of in-tree rust. Also a working linux travis conf
Remove unused code to support preffed-off and chrome-only APIs.
Remove compiler warnings from generated mako templates.
auto merge of #2657 : Ms2ger/servo/geckoisms, r=jdm
auto merge of #2660 : glennw/servo/mako-warnings, r=jdm
Divide check-ref targets into check-ref-cpu and check-ref-gpu

This allows us to run the CPU and GPU tests individually
Update snapshots to also build/test on OSX
Merge pull request #2671 from larsbergstrom/new_snapshots

Update to use snapshot builds
Request termination for XHR
Merge pull request #2656 from Manishearth/xhr-terminate

Request termination for XHR
Use internal mutability for XMLHttpRequest.
fixup! Use internal mutability for XMLHttpRequest.
fixup! Use internal mutability for XMLHttpRequest.