Add karma for testing (#2)

src/my-element.ts

@@ -15,7 +15,7 @@
 import { LitElement, html, customElement, property, css } from 'lit-element';
 
 @customElement('my-element')
-class MyElement extends LitElement {
+export class MyElement extends LitElement {
 
   static styles = css`
     :host {
@@ -36,7 +36,7 @@ class MyElement extends LitElement {
     return html`
       <h1>Hello, ${this.name}!</h1>
       <button @click=${this._onClick}>Click Count: ${this.count}</button>
-      <div class="slot"><slot></slot></div>
+      <slot></slot>
     `;
   }