Update setup.py, extend exclude mask
Update setup.py, extend exclude mask

otherwise it tries to install a packages called `examples` at top level, which is forbidden:

```
...
no previously-included directories found matching 'docs/_site'
no previously-included directories found matching 'docs/.sass-cache'
writing manifest file 'pyatv.egg-info/SOURCES.txt'
Copying pyatv.egg-info to /var/tmp/portage/dev-python/pyatv-0.7.4/image/_python3.8/usr/lib/python3.8/site-packages/pyatv-0.7.4-py3.8.egg-info
running install_scripts
Installing atvproxy script to /var/tmp/portage/dev-python/pyatv-0.7.4/image/_python3.8/usr/lib/python-exec/python3.8
Installing atvremote script to /var/tmp/portage/dev-python/pyatv-0.7.4/image/_python3.8/usr/lib/python-exec/python3.8
Installing atvscript script to /var/tmp/portage/dev-python/pyatv-0.7.4/image/_python3.8/usr/lib/python-exec/python3.8
 * ERROR: dev-python/pyatv-0.7.4::HomeAssistantRepository failed (install phase):
 *   Package installs 'examples' package which is forbidden and likely a bug in the build system.
 *
 * Call stack:
 *     ebuild.sh, line  125:  Called src_install
 *   environment, line 2971:  Called distutils-r1_src_install
 *   environment, line 1198:  Called _distutils-r1_run_foreach_impl 'distutils-r1_python_install'
 *   environment, line  445:  Called python_foreach_impl 'distutils-r1_run_phase' 'distutils-r1_python_install'
 *   environment, line 2587:  Called multibuild_foreach_variant '_python_multibuild_wrapper' 'distutils-r1_run_phase' 'distutils-r1_python_install'
 *   environment, line 2069:  Called _multibuild_run '_python_multibuild_wrapper' 'distutils-r1_run_phase' 'distutils-r1_python_install'
 *   environment, line 2067:  Called _python_multibuild_wrapper 'distutils-r1_run_phase' 'distutils-r1_python_install'
 *   environment, line  802:  Called distutils-r1_run_phase 'distutils-r1_python_install'
 *   environment, line 1166:  Called distutils-r1_python_install
 *   environment, line 1085:  Called die
 * The specific snippet of code:
 *               die "Package installs '${p}' package which is forbidden and likely a bug in the build system.";
 *
```
postlund/pyatv,postlund/pyatv