Silence Chef::Mixin::Language deprecation warnings

Quiet the deprecation warnings for Chef::Mixin::Language on newer versions of Chef.

```
[2014-06-02T17:55:36-04:00] WARN: Chef::Mixin::Language is deprecated. Use either (or both)
Chef::DSL::PlatformIntrospection or Chef::DSL::DataQuery instead.

[2014-06-02T17:55:36-04:00] WARN: Called from:
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:102:in `singletonclass'
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:101:in `<class:User>'
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:29:in `<class:GenericUsers>'
[2014-06-02T17:55:36-04:00] WARN: Chef::Mixin::Language is deprecated. Use either (or both)
Chef::DSL::PlatformIntrospection or Chef::DSL::DataQuery instead.

[2014-06-02T17:55:36-04:00] WARN: Called from:
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:130:in `singletonclass'
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:129:in `<class:GenericUsers>'
   /var/chef/cache/cookbooks/generic-users/libraries/user.rb:26:in `<top (required)>'
```