We fixed the gemspec and added the tarball fonctionnality

## Module naming
Now the name convention also works without a '/' on the mod, "puppetlabs/ntp" and "ntp" will result in the same "ntp" outcome 

## Tarball support
We are currently cleaning the tarball fonctionnality a little.

:tarball will work for a tar.gz from a remote url or from a local path
```
mod "module",
    :tarball => "http://yoursite.com/module.tar.gz"
```
or
```
mod "module",
   :tarball => "/home//slamont/module.tar.gz"
```