Update aboutus.md

Line 138 <div class="gantry-width-container">
Line 154 </div>

Line 190 <div class="gantry-width-container">
Line 213 </div>
Needs to be added, without them the contents would stack on top of each other not sit sided by side. This was observed through viewing the source demo code, compared with a fresh install of Joomla™, Gantry™ and this Plethora documentation.

CT
Merge pull request #148 from ulov/patch-1

Update aboutus.md