Packer (#172)

* introduce pako and add general packer interface

* add tests for packer

* use function API instead of class API for better tree shaking support

* refcatoring the rollup bundle config

typings/packer/base.d.ts

@@ -0,0 +1,7 @@
+import { eventWithTime } from '../types';
+export declare type PackFn = (event: eventWithTime) => string;
+export declare type UnpackFn = (raw: string) => eventWithTime;
+export declare type eventWithTimeAndPacker = eventWithTime & {
+    v: string;
+};
+export declare const MARK = "v1";

typings/packer/index.d.ts

@@ -0,0 +1,2 @@
+export { pack } from './pack';
+export { unpack } from './unpack';

typings/packer/pack.d.ts

@@ -0,0 +1,2 @@
+import { PackFn } from './base';
+export declare const pack: PackFn;

typings/packer/unpack.d.ts

@@ -0,0 +1,2 @@
+import { UnpackFn } from './base';
+export declare const unpack: UnpackFn;