Grammar correction, close #76
Fix arrow css problem

While dragging an arrow to the equipment window there is a problem with
a background-image. Remove it.
Update Intro.html
Updated README

Fixed typos and changed layout
Merge pull request #78 from jmduke/master

Fix typos in Intro.html
Edited prerequisites in README

As suggested by @vthibault
Merge pull request #79 from pybae/master

Updated README