fix linter errors

app/components/BookBuilder/Division.jsx

@@ -133,11 +133,11 @@ export class Division extends React.Component {
       addButtons = (
         <span>
           <AddButton
-            group="chapter"
+            group='chapter'
             add={_onAddClick}
           />
           <AddButton
-            group="part"
+            group='part'
             add={_onAddClick}
           />
         </span>
@@ -145,7 +145,7 @@ export class Division extends React.Component {
     } else {
       addButtons = (
         <AddButton
-          group="component"
+          group='component'
           add={_onAddClick}
         />
       )
@@ -177,7 +177,7 @@ export class Division extends React.Component {
           <div className={styles.separator} />
         </div>
 
-        <div id="displayed">
+        <div id='displayed'>
           { displayed }
         </div>
       </div>