add animations basics 1-6 (#120)

* add basics

* web: update dependencies

* TransferableTypeData added (#116)

* Updating index with new samples (#121)

* use arrow functions

* remove newline

* use verbs: random*() -> generate*()

* remove <Widget>[] type annotation on lists

* use raised button

* _route() => _createRoute()

* add parameter names to pageBuilder

* use the text theme's display1 for large text

* dispose animation controllers before calling super()

* remove local var

* use raised buttons instead of material buttons

* web: updated dependencies

* Added new test scripts (#122)

* add carousel, card_swipe, and focus_image samples (#119)

* add carousel, card_swipe, and focus_image samples

* fix image assets

* fix more asset images

* add repeating animation

* fix import

* add copyright headers

* remove Center widget

* imageAssetName

* use ClipRect, refactor _SwipeableCardState

* use offset.zero

* add comments

* remove reference to coverflow package

* change spread to toList()

* refactor coverflow sample

don't set width and height
use const
data -> images

* return widget directly, fix formatting

* inline transitionsBuilder

* image -> imageAssetName

* _rectTween() => _createTween()

* _expandToPageRoute -> _createRoute

* move non-updating widgets out of AnimatedBuilder

* code review updates to animations demos

animations/lib/src/misc/expand_card.dart

@@ -60,7 +60,7 @@ class _ExpandCardState extends State<ExpandCard>
               layoutBuilder:
                   (topChild, topChildKey, bottomChild, bottomChildKey) {
                 return Stack(
-                  children: <Widget>[
+                  children: [
                     Positioned.fill(
                       key: bottomChildKey,
                       child: bottomChild,