Gracefully Support Server Restart

[darkfrog26]

Many build environments allow the server to dynamically restart on code changes. This is a great help in increasing development efficiency, but it would appear as though SwaggerSocket does not like to gracefully restart. This should be as simple as providing cleanup functionality in the Servlet disposal method. For a test case of usage simply create an SBT web project and issue the command: "~;container:start; container:reload /" which will reload the container upon code change.