Fix an error with compatibility

I wanted to try muon, I installed it, and...

```
swistak35@raptop> gem install muon
Fetching: muon-0.0.1.gem (100%)
Successfully installed muon-0.0.1
1 gem installed
Installing ri documentation for muon-0.0.1...
Installing RDoc documentation for muon-0.0.1...

swistak35@raptop> cd one_of_my_projects

swistak35@raptop> muon init
You should include GLI::App instead
GLI.run no longer works for GLI-2, you must just call `run(ARGV)' instead
either fix your app, or use the latest GLI in the 1.x family
```

So, here is the fix. Or maybe I am just doing sth wrong.
Tests are passing : )

```
Started
...............
Finished in 0.083369 seconds.
15 tests, 29 assertions, 0 failures, 0 errors, 0 skips
```