Better Travis support

- removed Yast stubs, install real Yast instead
- run all tests at Travis
- `require` all files to report proper code coverage
This should not work as you use require which is not relative to current possition. see:
```
Dir["src/lib/**/*.rb"].each { |f| puts f }
src/lib/bootloader/device_map_dialog.rb
src/lib/bootloader/boot_record_backup.rb
src/lib/bootloader/device_map.rb
src/lib/bootloader/mbr_update.rb
src/lib/bootloader/udev_mapping.rb
src/lib/bootloader/grub2pwd.rb
src/lib/bootloader/grub2base.rb
```
Maybe you want to use:
```
Dir.chdir("src/lib") { Dir["**/*.rb"].each { |f| puts f } }
bootloader/device_map_dialog.rb
bootloader/boot_record_backup.rb
bootloader/device_map.rb
bootloader/mbr_update.rb
bootloader/udev_mapping.rb
bootloader/grub2pwd.rb
bootloader/grub2base.rb
```