message: rm checks to disallow adding middleware post-init
diff: @@ -105,11 +105,6 @@ Analytics.prototype.addIntegration = function(Integration) {
  */
  Analytics.prototype.addSourceMiddleware = function(middleware) {
  - if (this.initialized)
  - throw new Error(
  - 'attempted to add a source middleware after initialization'
  - );
  -
  this._sourceMiddlewares.add(middleware);
  return this;
  };
  @@ -122,11 +117,6 @@ Analytics.prototype.addSourceMiddleware = function(middleware) {
  */
  Analytics.prototype.addIntegrationMiddleware = function(middleware) {
  - if (this.initialized)
  - throw new Error(
  - 'attempted to add an integration middleware after initialization'
  - );
  -
  this._integrationMiddlewares.add(middleware);
  return this;
  };
  