202 http status code is handled as error

[ins429]

Twilio complete-room(update room) API returns 202 http status, while Parser.parse will handle 202 status as a error.
https://github.com/danielberkompas/ex_twilio/blob/master/lib/ex_twilio/parser.ex#L99-L102

I think it should return :ok just like 204 status.

e.g)

sid = "YOUR SID"
ExTwilio.Api.post!("https://video.twilio.com/v1/Rooms/#{sid}", %{status: "completed"})
#=>
%HTTPoison.Response{body: "{\"status\": \"completed\", \"unique_name\": \"<<ROOM SID>>\", \"date
_updated\": \"2018-05-21T19:37:53Z\", \"video_codecs\": [\"H264\"], \"max_participants\": 50, \"record_participants_on_connect\": true,
\"enable_turn\": true, \"account_sid\": \"<<ACOUNT SID>>\", \"url\": \"https://video.twilio.com/v1/Rooms/<<ROOM SID>>\",
\"end_time\": \"2018-05-21T19:38:31Z\", \"sid\": \"<<ROOM SID>>\", \"duration\": 39, \"
date_created\": \"2018-05-21T19:37:52Z\", \"media_region\": \"us1\", \"type\": \"group\", \"status_callback_method\": \"POST\", \"status
_callback\": \"https://pjlee.localtunnel.me/hooks/twilio/rooms\", \"links\": {\"recordings\": \"https://video.twilio.com/v1/Rooms/<<ROOM SID>>/Recordings\",
\"participants\": \"https://video.twilio.com/v1/Rooms/<<ROOM SID>>/Part
icipants\"}}",
headers: [{"Access-Control-Allow-Credentials", "true"},
 {"Access-Control-Allow-Headers",
  "Accept, Authorization, Content-Type, If-Match, If-Modified-Since, If-None-Match, If-Unmodified-Since"},
 {"Access-Control-Allow-Methods", "GET, POST, DELETE, OPTIONS"},
 {"Access-Control-Allow-Origin", "*"},
 {"Access-Control-Expose-Headers", "ETag"},
 {"Content-Type", "application/json"},
 {"Date", "Mon, 21 May 2018 19:38:31 GMT"},
 {"Twilio-Concurrent-Requests", "1"}, {"Twilio-Request-Duration", "0.020"},
 {"Twilio-Request-Id", "RQ0011b71af2b545f18b15c76d3f02dbbb"},
 {"X-Powered-By", "AT-5000"}, {"X-Shenanigans", "none"},
 {"Content-Length", "849"}, {"Connection", "keep-alive"}],
request_url: "https://video.twilio.com/v1/Rooms/<<ROOM SID>>",
status_code: 202}

PR: #98