Add a widgets.dart uber library

Now you can import 'package:sky/widgets.dart' to get all the widgets.

Rename some animation classes.

* Intentions => Behaviors
* SlideIn => SlideTransition
* FadeIn => FadeTransition
* removed unused AnimatedContainer intentions

Use transitions for Dismissable

Use SkImage instead of SkBitmap

Fix visual bugs in Stocks

Apparently SkImage is the new hotness.

Simplifies the code a bit.

Add support for FontStyle.italics

 - Center the labels on the tabs
 - Make the drawer's mask visible

Allow iOS apps to restart by copying the app.skyx to the Documents directory on the device.

directory on the device.

This work is to support a workflow where developers testing on an iOS
device will automatically see their app updates as they change their Sky
code. Currently this works by using the ios-deploy tool:
$ ios-deploy --bundle_id 'org.domokit.sky.game' --upload out/ios_Debug/game_app.app/app.skyx --to Documents/app.skyx
Upcoming commits will incorporate this into skytool.

Fix skyanalyzer

ScrollableBlock should be able to overscroll

Our supressions for the generated mojom.dart files weren't working after we
deleted the mojom package. This CL updates the filters to catch mojom.dart
files again.

When a ScrollableBlock can scroll, we want to be able to drag into the
overscroll region. Previously we could fling into the overscroll region, but we
couldn't actually drag there.

Remove sky:init

Now that we don't have a magicaly mojom package, we don't need sky:init.

Support borders with borderRadius

Add transitions.dart for common animation transitions.

Use those in SnackBar, Drawer, navigator instead of AnimatedContainer's
intentions.

Currently we support only borders with uniform color and width.

Use absolute URLs in sky/packages/sky/README.md

When this README.md is published to pub.dartlang.org, the base URL is
pub.dartlang.org. We need to use absolute URLs in order to get back to GitHub.

Fixes #417

Fix TextAlign.right

We were applying the style to the RenderInline but we actually needed to apply
it to the RenderParagraph. The lineHeight property had the same problem.

Make sky package depend on new sky_engine and sky_services

Don't upload things again in stage two

Bump versions of sky packages