feat: implement the version 4 of the protocol

See https://github.com/socketio/engine.io-protocol for the list of
changes.

Note: The 'base64-arraybuffer' dependency must now be explicitly
included by the client (not needed by the server).

Author: darrachequesne

.gitignore

@@ -1 +1,2 @@
 node_modules
+.nyc_output

Makefile

@@ -15,12 +15,12 @@ suite
         });
     }, { defer: true })
     .add('encode payload as string', (deferred) => {
-        parser.encodePayload([{ type: 'message', data: 'test1' }, { type: 'message', data: 'test2' }], true, () => {
+        parser.encodePayload([{ type: 'message', data: 'test1' }, { type: 'message', data: 'test2' }], () => {
             deferred.resolve();
         });
     }, { defer: true })
     .add('encode payload as binary', (deferred) => {
-        parser.encodePayload([{ type: 'message', data: 'test' }, { type: 'message', data: Buffer.from([1, 2, 3, 4]) }], true, () => {
+        parser.encodePayload([{ type: 'message', data: 'test' }, { type: 'message', data: Buffer.from([1, 2, 3, 4]) }], () => {
             deferred.resolve();
         })
     }, { defer: true })
@@ -32,15 +32,13 @@ suite
     })
     .add('decode payload from string', (deferred) => {
         let i = 0;
-        parser.decodePayload('6:4test16:4test2', () => {
-            if (++i === 2) deferred.resolve();
-        })
+        parser.decodePayload('test1\x1etest2');
+        deferred.resolve();
     }, { defer: true })
     .add('decode payload from binary', (deferred) => {
-        let i = 0;
-        parser.decodePayload(Buffer.from([0x00, 0x05, 0xff, 0x34, 0x74, 0x65, 0x73, 0x74, 0x01, 0x05, 0xff, 0x04, 0x01, 0x02, 0x03, 0x04]), () => {
-            if (++i === 1) deferred.resolve();
-        })
+        parser.decodePayload('test1\x1ebAQIDBA==', 'nodebuffer');
+        deferred.resolve();
+
     }, { defer: true })
     .on('cycle', function(event) {
         console.log(String(event.target));

benchmarks/index.js

@@ -0,0 +1,26 @@
+
+Current
+
+```
+encode packet as string x 175,944 ops/sec ±5.64% (25 runs sampled)
+encode packet as binary x 176,945 ops/sec ±16.60% (51 runs sampled)
+encode payload as string x 47,836 ops/sec ±9.84% (34 runs sampled)
+encode payload as binary x 123,987 ops/sec ±22.03% (53 runs sampled)
+decode packet from string x 27,680,068 ops/sec ±0.92% (89 runs sampled)
+decode packet from binary x 7,747,089 ops/sec ±1.65% (83 runs sampled)
+decode payload from string x 198,908 ops/sec ±27.95% (23 runs sampled)
+decode payload from binary x 179,574 ops/sec ±41.32% (23 runs sampled)
+```
+
+Results from parser v2 / protocol v3
+
+```
+encode packet as string x 228,038 ops/sec ±9.28% (40 runs sampled)
+encode packet as binary x 163,392 ops/sec ±8.72% (67 runs sampled)
+encode payload as string x 73,457 ops/sec ±14.83% (56 runs sampled)
+encode payload as binary x 71,400 ops/sec ±3.63% (75 runs sampled)
+decode packet from string x 22,712,325 ops/sec ±3.14% (90 runs sampled)
+decode packet from binary x 4,849,781 ops/sec ±1.27% (87 runs sampled)
+decode payload from string x 82,514 ops/sec ±49.93% (22 runs sampled)
+decode payload from binary x 149,206 ops/sec ±25.90% (76 runs sampled)
+```