Add token authentication

Hi Pascal,

first, great module, thanks.

This commit adds token authentication. Unfortunately i can't get the unit tests to work. Seems I use a different version of Karma/Grunt/Jasmin. Why not adding grunt and karma as dev dependency. That would solve this issue i guess.

Have fun
Stephan

Test output:
```
Running "karma:unit" (karma) task
WARN [config]: JASMINE is not supported anymore. Please use:
  module.exports = function(config) {
    config.set({
      // your config
      frameworks: ["jasmine"]
    });
  };

WARN [config]: JASMINE_ADAPTER is not supported anymore. Please use:
  module.exports = function(config) {
    config.set({
      // your config
      frameworks: ["jasmine"]
    });
  };

WARN [config]: LOG_INFO is not supported anymore.
  Please use `config.LOG_INFO` instead.
ERROR [config]: Config file must export a function!
  module.exports = function(config) {
    config.set({
      // your config
    });
  };
```