don't delete @@init

Author: echenley

src/instrument.js

@@ -236,10 +236,10 @@ function liftReducerWith(reducer, initialCommittedState, monitorReducer, options
       }
       case ActionTypes.PERFORM_ACTION: {
         if (options.maxAge && stagedActionIds.length === options.maxAge) {
-          // If maxAge has been reached, remove oldest action
-          delete actionsById[stagedActionIds[0]];
+          // If maxAge has been reached, remove oldest action.
+          delete actionsById[stagedActionIds[1]];
           skippedActionIds = skippedActionIds.filter(id => id !== stagedActionIds[0]);
-          stagedActionIds = stagedActionIds.slice(1);
+          stagedActionIds = [0].concat(stagedActionIds.slice(2));
           committedState = computedStates[1].state;
           computedStates = computedStates.slice(1);
         }