Fixed coveralls badge and typo in README.md

[ifraixedes]

No description provided.

[dougwilson]

I am already using the correct coveralls badge, the service just seems to be down. You changed it from SVG to a PNG one, which looks like garbage on high DPI displays.

[ifraixedes]

Ok, What about the typo? do I only send it?

[dougwilson]

I fixed the typo in the readme, thank you :)

[ifraixedes]

Your are welcome, at the end is the think that I wanted to report, by I though that the badge was wrong, for that reason I changed it, my apologies for that.

Thanks.

[dougwilson]

It's no problem. I did not know the reasoning behind the badge change. At first I was thinking you changed it because I had it pointing to the wrong repo :)