change rows in textarea demo to by dynamic

Author: Ales Rechtorik

src/demo-app/input/input-demo.html

@@ -93,7 +93,7 @@ <h4>With `rows` explicitly set</h4>
         placeholder="Textarea with autosize"
         class="demo-full-width"
         autosize
-        rows="8"
+        [rows]="rows"
         value="Hello world. How are you?">
       </md-textarea>
     </div>

src/demo-app/input/input-demo.ts

@@ -21,6 +21,7 @@ export class InputDemo {
     { value: 40 },
     { value: 50 },
   ];
+  rows = 8;
 
   addABunch(n: number) {
     for (let x = 0; x < n; x++) {