version to 0.5.0

* Add license to gemspec (6f2c170)
* Update benchmarking standards (0a93a4)
* Updated `Assert` and `DatWorkerPool` versions (7c1f94)
* Change `Server` to a class instead of a mixin (#25)
* Don't validate that min workers is less than max workers (#26)
* Rename the `run` command to `start` (#27)
* Change the `wait_for_shutdown` default from true to false (#28)
* Proxy `TCPServer` in module, cleanup `listen` method (#29)
* Use `Mutex` lock on signal querying (#30)
* Clean up `Server`'s public methods that should be private (#31)
* Remove `accept_connection` loop, not needed (#32)
* Rework `Server` unit tests to use stubbing and a spy (#33)
* Remove callbacks, keep configuring `TCPServer` ability (#34)
* Use self-pipe trick for stopping, halting and pausing (#35)
* Reset benchmarks to new baseline (fa202f)
* Don't use Rake for the benchmarking scripts (#39)
* Switch to the latest assert for test stubbing (#41)
* Update the README to reflect the new DatTCP features (#40)
* Minor cleanups (c5906a)