structural changes to support Iframes
handle pipeline exiting properly
navigation bug fix
switched window.page from *mut Page to @mut Page
removed a call to copy in servo.rc and renamed NavigationContext.navigate ==> NavigationContext.load
remove unused arg from script_task::handle_navigate_msg

remove unnecessary commented-out code
fix borrow check failures by reverting to storing *mut Page in window
updated rust-http-client submodule
auto merge of #628 : tkuehn/servo/master, r=metajack

Completed:
  * Replace pipeline navigation context with frame tree navigation context
  * Reuse script task for same origin iframes
  * Block on size future for iframe reflow
  * Remove global script context
  * Change codegen to use specific page context rather than script context.

Still to do:
  * Compositor's handling of relative frame positions
  * Compositor currently only asks for tiles from outermost frame
  * Window events are forwarded to the outermost frame's script. Should be routed to proper script via constellation.
  * Layout's sending of updated iframe sizes to constellation or size future (initial size only) as reflow is performed
constellation blocks on compositor before sending permission to paint to renderers
refactored for more code reuse in constellation
auto merge of #638 : tkuehn/servo/master, r=metajack

... renderers
FIXME: uint::range to vec`s iter().advance
auto merge of #640 : recrack/servo/fixme_each_mut, r=jdm
Generate HTMLDocument bindings. Introduce invariant into generated bindings that associated DOM classes are named the same as their interfaces, so Event and Event_ need to be swapped.
auto merge of #641 : jdm/servo/htmldoc2, r=jdm

There are several mechanical changes here that make this look more intimidating than it is. DOMStrings are now passed by reference, and Event and Event_ have swapped names. Finally, there are the various places that need to use `document.with_base |doc| { document.foo }` instead of `document.foo`.
Generate bindings for Window.
auto merge of #645 : jdm/servo/window, r=jdm

This one also looks larger than necessary because GetParentObject needed to be changed to return an Option.