Properly fix the download button

All other <button> elements were already handled by the JS script
so the choice was made to drop the onclick tags on them. Sadly, the
download button was missed. This commit properly fixes that.

index.html

@@ -88,7 +88,7 @@
    </table>
   </form>
   <div class="downloadbuttons">
-   <button id="bdownload" class="mdl-button mdl-js-button mdl-button--fab mdl-js-ripple-effect mdl-button--colored" onclick="javascript:downloadSubmit();" disabled><i class="material-icons">file_download</i></button>
+   <button id="bdownload" class="mdl-button mdl-js-button mdl-button--fab mdl-js-ripple-effect mdl-button--colored" disabled><i class="material-icons">file_download</i></button>
    <div id="github-latest"><div id="github-progressbar" class="mdl-progress mdl-js-progress mdl-progress__indeterminate progress-demo"></div><span class="mdl-typography--caption-color-contrast">querying GitHub API...</span></div>
    <button id="bversion" class="mdl-button mdl-js-button mdl-button--accent" disabled>Version Information</button><br />
    <button id="bmd5" class="mdl-button mdl-js-button mdl-button--accent" disabled>MD5 Checksum</button><br />