Registering email to html

Here I changed the plain text email you recive when registering with something more appealing. It use the black logo, so maybe we should move the image to another host to save bandwith?

I think it looks pretty cool compared with the plain text mail while keeping it simplicity. It provides a professional look and make your emails quickly recognizable thanks to the logo. 
Maybe you could change the button text to something like "Log in" or "Start playing" rather than "activate your account"

What do you think about it? Here is a picture of it on gmail :)
![email](https://cloud.githubusercontent.com/assets/6611118/3353725/ce31c7dc-fa8a-11e3-8ddb-80801782c1c0.png)