fix style of the update box

[grahamjeffries]

Add style for the update element. Add consistent spacing for a few other entries.

[grahamjeffries]

It seems that the mec.css needs to be updated for the polls app in Chapter 14, too. Something like

...
#polls {
  margin-left: 20px;
}

#polls h1 {
  text-align: center;
}
...