Fix lint errors

addon/capture-data.js

@@ -1,3 +1,5 @@
+/* globals captureText, Readability */
+
 (function () {
   const SCREENSHOT_WIDTH = 350;
 
@@ -37,7 +39,7 @@
   async function onMessage(message) {
     if (message.type !== "getData") {
       console.warn("Unexpected message type:", message.type);
-      return;
+      return undefined;
     }
     browser.runtime.onMessage.removeListener(onMessage);
     let data = {

addon/emailTemplates.jsx

@@ -65,12 +65,12 @@ this.emailTemplates = (function () {
 
   class JustLinks extends React.Component {
     render() {
-      let tabList = this.props.tabs.map(tab => {
+      let tabList = this.props.tabs.map((tab, index) => {
         let selection =  null;
         if (tab.selection) {
           selection = <Fragment>{selectionDisplay(tab.selection)} <br /><br /></Fragment>;
         }
-        return <Fragment>
+        return <Fragment key={index}>
           <a href={tab.url}>{tab.title}</a> <br />
           { selection }
         </Fragment>;
@@ -93,7 +93,7 @@ this.emailTemplates = (function () {
           let hr = index === this.props.tabs.length - 1 ? null : <hr />;
           readability = <Fragment><div dangerouslySetInnerHTML={{__html: tab.readability.content}} /> { hr }</Fragment>;
         }
-        return <Fragment>
+        return <Fragment key={index}>
           <a href={tab.url}>{tab.title}</a> <br />
           { selection }
           { readability }

addon/popup.jsx

@@ -185,8 +185,8 @@ class TemplateItem extends React.Component {
     if (this.props.selected) {
       className += " selected";
     }
-    return <li className={className} onClick={this.selectTemplate.bind(this)} role="button">
-      {this.props.title}
+    return <li className={className}>
+      <button onClick={this.selectTemplate.bind(this)}>{this.props.title}</button>
     </li>;
   }