$http.defaults.headers.common['Auth-Token'] = 'token';

$http.defaults.headers.common['Authentication'] = 'authentication';

myapp.factory('httpRequestInterceptor', function () {
  return {
    request: function (config) {

      // use this to destroying other existing headers
      config.headers = {'Authentication':'authentication'}

      // use this to prevent destroying other existing headers
      // config.headers['Authorization'] = 'authentication;

      return config;
    }
  };
});

myapp.config(function ($httpProvider) {
  $httpProvider.interceptors.push('httpRequestInterceptor');
});