move YaST class to SUSE::Connect module

Changing `class SUSE::Connect::YaST` to
```ruby
module SUSE
  module Connect
    class YaST
```
fixes `uninitialized constant Class::Client, ["/usr/lib64/ruby/gems/2.0.0/gems/suse-connect-0.0.14/lib/suse/connect/yast.rb:40:in activate_product'" ...` error.