Fixed readme link

```
$ curl https://raw.github.com/garygolden/bash_colors/master/bash_colors.sh
<html><body>You are being <a href="https://raw.github.com/maxtsepkov/bash_colors/master/bash_colors.sh">redirected</a>.</body></html>

$ curl https://raw.github.com/maxtsepkov/bash_colors/master/bash_colors.sh
#!/bin/bash
#
# Constants and functions for terminal colors.
# Author: Max Tsepkov <max@garygolden.me>
...
```