Pin `package:test` to an exact revision

We use a number of non-public APIs in the test package, which makes our
dependency quite fragile. This patch pins a specific, known-good version. We
should update to the lastest version in a follow-up patch.

ignore .atom directories

Start working on a TimePicker

Improve unauthorized regexp

Fixes https://github.com/flutter/flutter.github.io/issues/101

Expose the navigator in routes.

You can't actually pick a time with the time picker yet, but this patch adds
most of the plumbing.

Add drop down buttons to Material Gallery

Integrate Date Picker into material_gallery

Fix upload of composited scene with non-zero offsets

We weren't correctly offsetting the clips when uploading composited scenes. Now
we apply the proper offsets.

Allow run_mojo --android to specify location of flutter engine

Add package:flutter_test

This package contains WidgetTester, which is very useful when writing tests for
widgets.

Make it possible to run tests outside the Flutter repo

Add avatars to material chips

Fixes #464

This patch still requires a locally built engine. I'll remove the need for a
locally built engine in a future patch.

Fixes #278

Add basic support for material chips

http://www.google.com/design/spec/components/chips.html#chips-behavior

This patch adds support for deletable and non-deleteable chips, but doesn't yet
add support for contact chips. Also, demo the chips in a new Material Gallery
app that will let us demo our gallery of widgets in a single app.

more verbose error message

Avoid using transforms when simple offsets will do.

Rev engine, services, and sdk.

Clean up the term "modal" in the navigator

Provide a way to insert multiple overlays at once.

Assert: don't push a PageRoute over a PopupRoute.

"Fixes" #389.

Now we only use it for things related to ModalRoute and ModalBarrier.

(This is easy now that ephemeral routes are gone, so there's no other
kind of route to distinguish against.)

Fix analyzer warnings

Should make Travis green again. Also, add better logging to
dev/update_packages.dart.