rsyslog: make all module params configurable

+ support false for *_package_name variables. This is useful if relp
support is not necessary as it happens that no packages exist for
RedHat < 6.

All these changes should be fully backward compatible.
use rsyslog::snippet for client and server configs

Doesn't feature any functional change, but it seems cleaner to use
that definition to avoid repeating dependencies and paths.
Create log directories with same ownership as files
it doesn't make sense to test classes that are never included directly
added a default site.pp (require to test defined type) + adapt. .gitignore
travis: small improvements
Gemfile: upgraded gem puppetlabs_spec_helper + cosmetics
Gemfile instead of .gemfile
Merge pull request #30 from mbornoz/improvements

Improvements