Handle onChange event and upload file.

lib/components/UploadPage.js

@@ -36,6 +36,13 @@ export default class UploadPage extends React.Component {
     UploadActions.uploadFile(file)
   }
 
+  handleSelectedFile(event) {
+    let files = event.target.files;
+    if (files.length > 0) {
+      UploadActions.uploadFile(files[0]);
+    }
+  }
+
   render() {
     switch (this.state.status) {
       case 'ready':
@@ -50,7 +57,7 @@ export default class UploadPage extends React.Component {
             <p>Drag the file into this window to get started.</p>
             <p>Or
             <label className="myLabel">
-              <input type="file" required/>
+              <input type="file" onChange={this.handleSelectedFile} required/>
               <span>select a file</span>
             </label>
             .