Changed guard-test for guard-minitest

- The reason is that it's seems Rails 4 uses minitest as default
- The repeated tests error has not been solved

There's a non support issue with zeus and the gem guard-minitest. I've added the functionality but only in my local gem (I'll see if it's an issue of the gem and in this case I'll open an issue and maybe do a PR to its repository).

By now, (easier if you have the bundler installed into the project folder) you can replace:

```
guard-minitest-0.5.0/lib/guard/minitest/runner.rb
```

with the content of this [gist](https://gist.github.com/jd-erreape/493f244bab4804d777ba) and you should be ok