Implement Attr#nodeValue

Fixes #4047
Updated to expect tests that are now passing
Remove unused exit after load option.

This simplifies some upcoming changes to how event handling works.
Make glutin work on mac.

- Update glutin, and update rust-cocoa to use the servo fork now that upstream is up to date.
- Many events and resizing are still not working correctly on mac yet.
auto merge of #4051 : glennw/servo/remove-exit-load, r=mbrubeck

This simplifies some upcoming changes to how event handling works.
auto merge of #4050 : mttr/servo/implement_attr_nodevalue, r=Ms2ger

Fixes #4047, and updates to expect tests that are now passing because of it.
Allow reftests to be run directly w/ relative path

Fixes #3521
auto merge of #4053 : mttr/servo/reftests_with_relative_dir, r=SimonSapin

Fixes #3521
No longer need for local variable in PropertyDeclaration::parse
Arc::make_unique is now stable
auto merge of #4056 : brunoabinader/servo/css-updates, r=SimonSapin

TSIA
auto merge of #4052 : glennw/servo/update-glutin, r=larsbergstrom

- Update glutin, and update rust-cocoa to use the servo fork now that upstream is up to date.
- Some events and resizing are still not working correctly on mac yet.
Run a single WPT test from a relative path

Fixes #4055
embedding: fix type decls
embedding: add cef_display_handler_t decl
embedding: add cef_life_span_handler_t decl
embedding: add cef_client_t decl
embedding: add cef_window_info_t decl
util::opts::default_opts() is now pub
embedding: redo browser creation and message loop code to be more CEF-like

big thanks to @alexcrichton for his help with this