Type improvements (#706)

* use nanobus for the emitter typings

instead of `events`, which is a bit different

* add typings for `cache` option

index.d.ts

@@ -1,13 +1,11 @@
-/// <reference types="node" />
-
-import * as EventEmitter from 'events'
+import Nanobus = require('nanobus')
 
 export = Choo
 
 declare class Choo {
   constructor (opts?: Choo.IChoo)
-  use (callback: (state: Choo.IState, emitter: EventEmitter, app: this) => void): void
-  route (routeName: string, handler: (state: Choo.IState, emit: (name: string, ...args: any[]) => void) => void): void
+  use (callback: (state: Choo.IState, emitter: Nanobus, app: this) => void): void
+  route (routeName: string, handler: (state: Choo.IState, emit: Nanobus['emit']) => void): void
   mount (selector: string): void
   start (): HTMLElement
   toString (location: string, state?: Choo.IState): string
@@ -18,6 +16,12 @@ declare namespace Choo {
     history?: boolean
     href?: boolean
     hash?: boolean
+    cache?: number | ICache
+  }
+
+  export interface ICache {
+    get(id: string | number): undefined | null | any
+    set(id: string | number, element: any): void
   }
 
   export interface IState {