Fixing encoding issues on Windows systems with version 3.6.0

This is the disallowed characters in filenames on Windows:

![screenshot_5_28_13_9_43](https://f.cloud.github.com/assets/334273/571223/61beec90-c770-11e2-9c8c-376361bc1b3b.png)

We had a filename that included one of those, which makes the gem unusable on Windows platforms. 

Reported in issue #145