Cleanup SecurityConfiguration

- Clean imports
- Remove unnecessary rememberMeServices() since this is already created via
  classpath scanning
- Remove unnecessary RememberMeAuthenticationProvider. This is already
  created via http.rememberMe().rememberMeServices()
- Remove unnecessary authenticationManager() Bean. This is not necessary
  since the AuthenticationManagerBuilder is being used
- Removed unnecessary UserDetailsService since this is already created via
  classpath scanning
- Use global AuthenticationManagerBuilder to expose to method security
Merge pull request #2 from rwinch/security-configuration-cleanup

Cleanup SecurityConfiguration