Don't install dummyserver into site-packages

It is pure example code with self-signed certificates. It pollutes the
global site-packages spaces and is potentially dangerous (if used
accidentally). It doesn't make sense to install it as 'package_data' or
'date_files' either. Since it servers as an example it should be part
of the source distribution.
Merge pull request #362 from saschpe/master-dummyserver-as-docs

Don't install dummyserver into site-packages