Support base64 encoding on bulk writes

[joelhoffman]

Following the test here it looked like it was supported, but this didn't work:

https://github.com/flightstats/hub/blob/master/src/test/java/com/flightstats/hub/dao/aws/MultiPartParserTest.java

POST /channel/joeltest/bulk HTTP/1.1
Accept-Encoding: gzip
User-Agent: Jetty/9.2.13.v20150730
Accept: application/json
Content-Type: multipart/mixed; boundary="=_="
Host: hub.svc.dev
Transfer-Encoding: chunked

--=_=
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: base64

dGVzdAo=

--=_=--

GET /channel/joeltest/2015/12/17/22/36/59/458/0E19OB000000 HTTP/1.1
Host: hub.svc.dev
User-Agent: curl/7.43.0
Accept: */*

HTTP/1.1 200 OK
Date: Thu, 17 Dec 2015 22:39:42 GMT
Content-Type: text/plain;charset=utf-8
Creation-Date: 2015-12-17T22:36:59.458Z
Link: <http://hub.svc.dev/channel/joeltest/2015/12/17/22/36/59/458/0E19OB000000/previous>;rel="previous"
Link: <http://hub.svc.dev/channel/joeltest/2015/12/17/22/36/59/458/0E19OB000000/next>;rel="next"
Vary: Accept-Encoding
Server: Hub/12-17.1.s3-single
Content-Length: 8

dGVzdAo=

[moulliet]

@joelhoffman what result were you expecting?

[joelhoffman]

5 bytes: 74, 65, 73, 74, 0a (test\n)

[joelhoffman]

Alternately, a Content-Transfer-Encoding: base64 header on the response payload.