Implement clear for floats
Remove gunk between tiles after zoom
auto merge of #732 : eschweic/servo/tile-grunge, r=metajack

Gets rid of that annoying grit that appears between tiles after zooming.
auto merge of #727 : metajack/servo/clear-float, r=metajack

Rebased #715
Remove rust-glut
Update submodules for new Rust version
Linter changes
Trait changes, and eliminate 'copy'
Library changes
Convert our iterators to external iterators

Except util/tree.rs (see next commit).
Reorganize tree ref / node traits

rustc is no longer happy with

    impl<NR:TreeNodeRef<N>,N:TreeNode<NR>> TreeUtils for NR
For loops and misc changes
Stub out some things that need changes for newrt

brson and I will work on these next.
Remove HTTP support (!)

We'll need a new HTTP client lib written against newrt.
Update Rust version again

This gets us the new runtime.
Un-stub timer code
Put the compositor on the main thread in the newrt way
Include a dummy main() with the test harness