Support Svelte 3

fixes #546, #551, #552, #554

test/apps/layout/src/routes/[x]/[y]/[z].html

@@ -1,20 +1,18 @@
-<span>z: {segment} {count}</span>
-<a href="foo/bar/qux">click me</a>
-
-<script>
+<script context="module">
 	import counts from '../_counts.js';
 
-	export default {
-		preload() {
-			return {
-				count: counts.z += 1
-			};
-		},
+	export function preload() {
+		return {
+			count: counts.z += 1
+		};
+	}
+</script>
 
-		oncreate() {
-			this.set({
-				segment: this.get().params.z
-			});
-		}
-	};
-</script>
+<script>
+	import { page } from '@sapper/app';
+
+	export let count;
+</script>
+
+<span>z: {$page.params.z} {count}</span>
+<a href="foo/bar/qux">click me</a>

test/apps/layout/src/routes/[x]/[y]/_layout.html

@@ -1,22 +1,21 @@
-<span>y: {segment} {count}</span>
-<svelte:component this={child.component} {...child.props}/>
-
-<span>child segment: {child.segment}</span>
-
-<script>
+<script context="module">
 	import counts from '../_counts.js';
 
-	export default {
-		preload() {
-			return {
-				count: counts.y += 1
-			};
-		},
+	export function preload() {
+		return {
+			count: counts.y += 1
+		};
+	}
+</script>
 
-		oncreate() {
-			this.set({
-				segment: this.get().params.y
-			});
-		}
-	};
-</script>
+<script>
+	import { page } from '@sapper/app';
+
+	export let count;
+	export let child;
+</script>
+
+<span>y: {$page.params.y} {count}</span>
+<svelte:component this={child.component} {...child.props}/>
+
+<span>child segment: {child.segment}</span>