Some minor improvements/fixes:

* Removed Ubuntu from data.pp as it is not an $::osfamily
* $stunnel::data::cert_dir is created when the stunnel::cert define is called
* /usr/local/bin/stunnel-combine-certs is now distributed when the stunnel::cert define is called
* Debian systems now install the "stunnel4" package; when trying to install "stunnel" puppet trys to install metapackage on each run which is already present
* Fixes for puppet-lint