Corrected typo in footer.php

Developpement-----> Development
Add missing { in main.css

.img > img class had closing } but no starting {
Made the heading 'TheOpenCodex' more responsive

enclosed the contents of
<div class="jumbotron">
with the container class
Merge pull request #1 from salehgeek/patch-1

Corrected typo in footer.php
Merge pull request #7 from salehgeek/master

Added missing { to main.css