Explicitly check for postback instead of defaulting to it when prepar…

…ing the response to a request. This fixes #7

lib/sagas/requests/index.js

@@ -330,7 +330,7 @@ export function * performCallback (request, response) {
   const callbackUrl = URL(request.callback_url)
   const redirectUrl = request.redirect_url ? URL(request.redirect_url) : undefined
 
-  if (request.postback !== false || callbackUrl.hostname.match(/^(chasqui|api)\.uport\.(me|space)$/)) {
+  if (request.postback === true || callbackUrl.hostname.match(/^(chasqui|api)\.uport\.(me|space)$/)) {
     yield call(postBackToServer, request, response)
     if (redirectUrl !== undefined) {
       return yield call(returnToApp, redirectUrl, undefined)