Enable/Unprefix Animations & Transitions, add basic tests

sky/tests/animation/basic-imperative.sky

Index: sky/tests/animation/basic-imperative.sky
diff --git a/sky/tests/animation/basic-imperative.sky b/sky/tests/animation/basic-imperative.sky
new file mode 100644
index 0000000000000000000000000000000000000000..2a185cb18ecf8bc05de3707a8e94cf06c3da178d
--- /dev/null
+++ b/sky/tests/animation/basic-imperative.sky
@@ -0,0 +1,16 @@
+<sky>
+<import src="../resources/chai.sky" />
+<import src="../resources/mocha.sky" />
+<div id="example">Hello, Sky</div>
+<script>
+var example = document.getElementById('example');
+
+describe('Element.animate opacity', function() {
+  it('should amimate from 0 to 1', function() {
+    example.animate([{ opacity: 0 }, { opacity: 1}], 2000);
+    internals.pauseAnimations(.5);
+    assert.equal(.25, getComputedStyle(example).opacity);
+  });
+});
+</script>
+</sky>