Add User Login Endpoint

[pauljamescleary]

https://github.com/ariesprayoga/swagger-java-sample-app/blob/master/src/main/java/com/wordnik/swagger/sample/resource/UserResource.java

[pauljamescleary]

depends on #49

[pauljamescleary]

A login endpoint does exist that generates a password hash. Have to tie this together with JWT to send the logged in token down to the browser (as well as authenticate subsequent requests). Need a logout endpoint to expire the token.