Allow event data/metadata to be stored as JSON array through HTTP API

[shaan1337]

Sending an event with data/metadata as JSON array through the HTTP API does not work, it results in an empty string:

curl -i -d @event.txt -H "Content-Type:application/vnd.eventstore.events+json" "http://127.0.0.1:2113/streams/stream"

event.txt:

[
  {
    "eventId": "fbf4a1a1-b4a3-4dfe-a01f-ec52c34e1717",
    "eventType": "event",
    "data": [{"a":1},{"b":2}],
    "metadata": [{"c":3},{"d":4}]
  }
]

However, JSON arrays work fine with .NET API:

_conn.AppendToStreamAsync(
    "stream",ExpectedVersion.Any,
    new EventData[]{
        new EventData(
            Guid.NewGuid(),
            "type",
            true,
            Encoding.ASCII.GetBytes("[{},{}]"),
            Encoding.ASCII.GetBytes("[{},{}]"))
    }).Wait();

[avish0694]

Tested before and after the commit, It works as expected.