Concat every subcommand of a command into a single file

* now uses puppetlabs-concat
* no public API changes

```
Finished in 29.21 seconds
156 examples, 0 failures

Total resources:   22
Touched resources: 22
Resource coverage: 100.00%
```
Upgrade version in Modulefile
Update CHANGELOG for v2.1.0
Remove useless "if defined" surrounding "include xinetd"
Final v2.1.0 release

* Remove useless `if defined` surrounding `include xinetd` in `server.pp`
* Final _CHANGELOG_ modifications
* require rspec < 3.0.0 for test suite as rspec-puppet seems to have no support for 3.x version