Include wrapper scripts when creating avocado-examples package.

Include all examples/wrappers/*.sh scripts when building
the `avocado-examples` package. The scripts will live under
`/usr/share/avocado/wrappers` when installed.

Signed-off-by: Rudá Moura <rmoura@redhat.com>
Merge pull request #284 from ruda/wrappers_packaging

Include wrappers script when creating `avocado-examples` package.