fix(dccd): fix DirtyCheckingRecord.toString() throws an exception

closes #1057
chore(pubspec): bump SDK version (>= 1.4.0)

Closes #1009
fix(transcluding_component_factory): fix content detach logic

detachContent was finding the wrong end comment node and failing on assetion (in checked mode).
test(MockHttpBackend): Add named parameters to MockHttpBackend.call
feat(Http): Http service can make cross-site requests (get, post, put, etc.) which use credentials (such as cookies or authorization headers).

Closes #945
Closes #1026
fix(element binder): Ensure mappings are evaluated before attach() is
called.

Closes #1059
chore: Use SauceLabs to run tests in the cloud.

Closes #982
Don't install FF and Chrome