HomeBridge crashed by "TypeError: body.filter is not a function"
Hi, this library is very useful and convenient for my Sonoff Basic but however I found that this library caused my HomeBridge to crash randomly after Home app on iPhone trying to refresh accessories status.

Here's the log
```
[2018-7-30 19:02:21] [eWeLink] WebSocket was closed. Reason [1006]
WebSocketClient: reconnecting...
[2018-7-30 19:02:28] [eWeLink] Sending login request [{"action":"userOnline","us                             erAgent":"app","version":6,"nonce":"153295214845100","apkVesrion":"1.8","os":"io                             s","at":"047e6b963a148e143401f5f373f040xxxxxxxxxx","apikey":"2817695a-3b73-4cd4-                             940a-19xxxxxxxxxx","ts":"1532952148","model":"iPhone10,6","romVersion":"11.1.2",                             "sequence":1532952148451}]
[2018-7-30 19:02:28] [eWeLink] WebSocket messge received:  {"error":0,"apikey":"                             2817695a-3b73-4cd4-940a-19xxxxxxxxxx","config":{"hb":1,"hbInterval":145},"sequen                             ce":"1532952148451"}
WebSocketClient: retry in 5000ms 1006
[2018-7-30 19:05:08] [eWeLink] WebSocket was closed. Reason [1006]
WebSocketClient: reconnecting...
[2018-7-30 19:05:14] [eWeLink] Sending login request [{"action":"userOnline","us                             erAgent":"app","version":6,"nonce":"153295231499200","apkVesrion":"1.8","os":"io                             s","at":"047e6b963a148e143401f5f373f040xxxxxxxxxx","apikey":"2817695a-3b73-4cd4-                             940a-19xxxxxxxxxx","ts":"1532952314","model":"iPhone10,6","romVersion":"11.1.2",                             "sequence":1532952314992}]
[2018-7-30 19:05:15] [eWeLink] WebSocket messge received:  {"error":0,"apikey":"                             2817695a-3b73-4cd4-940a-19xxxxxxxxxx","config":{"hb":1,"hbInterval":145},"sequen                             ce":"1532952314992"}
WebSocketClient: retry in 5000ms 1006
[2018-7-30 19:07:55] [eWeLink] WebSocket was closed. Reason [1006]
WebSocketClient: reconnecting...
[2018-7-30 19:08:01] [eWeLink] Sending login request [{"action":"userOnline","us                             erAgent":"app","version":6,"nonce":"153295248149300","apkVesrion":"1.8","os":"io                             s","at":"047e6b963a148e143401f5f373f040xxxxxxxxxx","apikey":"2817695a-3b73-4cd4-                             940a-19xxxxxxxxxx","ts":"1532952481","model":"iPhone10,6","romVersion":"11.1.2",                             "sequence":1532952481493}]
[2018-7-30 19:08:01] [eWeLink] WebSocket messge received:  {"error":0,"apikey":"                             2817695a-3b73-4cd4-940a-19xxxxxxxxxx","config":{"hb":1,"hbInterval":145},"sequen                             ce":"1532952481493"}
WebSocketClient: retry in 5000ms 1006
[2018-7-30 19:10:41] [eWeLink] WebSocket was closed. Reason [1006]
WebSocketClient: reconnecting...
[2018-7-30 19:10:47] [eWeLink] Sending login request [{"action":"userOnline","us                             erAgent":"app","version":6,"nonce":"153295264794300","apkVesrion":"1.8","os":"io                             s","at":"047e6b963a148e143401f5f373f040xxxxxxxxxx","apikey":"2817695a-3b73-4cd4-                             940a-19xxxxxxxxxx","ts":"1532952647","model":"iPhone10,6","romVersion":"11.1.2",                             "sequence":1532952647943}]
[2018-7-30 19:10:48] [eWeLink] WebSocket messge received:  {"error":0,"apikey":"                             2817695a-3b73-4cd4-940a-19xxxxxxxxxx","config":{"hb":1,"hbInterval":145},"sequen                             ce":"1532952647943"}
[2018-7-30 19:11:37] [eWeLink] Requesting power state for [Sonoff 1]
[2018-7-30 19:11:37] [eWeLink] Requesting power state for [Sonoff 1]
[2018-7-30 19:11:38] [eWeLink] Device [Sonoff 1] was reported to be offline by the API
[2018-7-30 19:11:38] [eWeLink] Requesting power state for [Sonoff 2]
[2018-7-30 19:11:39] [eWeLink] Device [Sonoff 2] was reported to be offline by the API
[2018-7-30 19:11:39] [eWeLink] Requesting power state for [Sonoff 1]
[2018-7-30 19:11:39] [eWeLink] Requesting power state for [Sonoff 2]
[2018-7-30 19:11:39] [eWeLink] Device [Sonoff 2] was reported to be offline by the API

/usr/lib/node_modules/homebridge-ewelink/node_modules/request-json/main.js:74
    return callback(error, response, parsed);
           ^
TypeError: body.filter is not a function
    at /usr/lib/node_modules/homebridge-ewelink/index.js:364:37
    at Object.parseBody (/usr/lib/node_modules/homebridge-ewelink/node_modules/request-json/main.js:74:12)
    at Request._callback (/usr/lib/node_modules/homebridge-ewelink/node_modules/request-json/main.js:148:26)
    at Request.self.callback (/usr/lib/node_modules/homebridge-ewelink/node_modules/request/request.js:186:22)
    at emitTwo (events.js:126:13)
    at Request.emit (events.js:214:7)
    at Request.<anonymous> (/usr/lib/node_modules/homebridge-ewelink/node_modules/request/request.js:1163:10)
    at emitOne (events.js:116:13)
    at Request.emit (events.js:211:7)
    at IncomingMessage.<anonymous> (/usr/lib/node_modules/homebridge-ewelink/node_modules/request/request.js:1085:12)

```