Error: "value" required in setHeader("Content-Type", value)

[tripott]

Will submit PR to help fix.

Stack trace:

_http_outgoing.js:502
    throw new Error('"value" required in setHeader("' + name + '", value)');
    ^

Error: "value" required in setHeader("Content-Type", value)
    at validateHeader (_http_outgoing.js:502:11)
    at ServerResponse.setHeader (_http_outgoing.js:511:3)
    at ServerResponse.writeHead (_http_server.js:209:21)
    at ClientRequest.<anonymous> (/Users/wottinger/Dropbox/JRS/code/pouch-offline-api/node_modules/express-couch-proxy/index.js:68:13)
    at Object.onceWrapper (events.js:316:30)
    at emitOne (events.js:115:13)
    at ClientRequest.emit (events.js:210:7)
    at HTTPParser.parserOnIncomingClient [as onIncoming] (_http_client.js:564:21)
    at HTTPParser.parserOnHeadersComplete (_http_common.js:116:23)
    at TLSSocket.socketOnData (_http_client.js:453:20)