Add a submodule for rust-cssparser

Even though this parser is not used yet, having it built
and tested with the rest of Servo helps ensure it does not bitrot.
auto merge of #568 : SimonSapin/servo/rust-cssparser-in-tree, r=metajack

[As discussed](https://github.com/mozilla/servo/wiki/Meeting-2013-07-01#css), even though this parser is not used yet, having it built and tested with the rest of Servo helps ensure it does not bitrot.
Fix replaceFileIfMissing return value.
Bindings gen touches output Rust files to prevent it from running every time.
auto merge of #574 : metajack/servo/bindgen-deps, r=jdm

This touches the `.rs` files even if they don't change. This will cause libscript to rebuild sometimes even when it doesn't have to. This seems better than having bindgen run every time as the case where CodegenRust.py changes but doesn't change the output `.rs` seems like it should be rare.

r? @jdm
Fix build failure in make check-content
auto merge of #559 : tkuehn/servo/master, r=metajack

r? @metajack this includes the rust-azure pointer change
auto merge of #575 : kmcallister/servo/check-content, r=metajack
Make quadtrees generic
Address pcwalton's comments
Implement progressive rendering
Clean up and annotations
Cleanup after merge
Fix paint permissions issue, clean up
Address metajack's comments
Move buffer requests to quadtree; add remove_tile() to quadtree; automatic rerendering after pinch-zoom
Address pcwalton's nits; automatic rendering after scrolling
auto merge of #557 : eschweic/servo/master, r=pcwalton

The compositor now keeps track of what has been rendered and what needs rendering based on the window rect, and asks the renderer for tiles only when needed.
WIP iframe handling.
refactored url handling code in script task to be more idiomatic