allow downloading of JSON via the UI
use ConversationApiView (thanks @jerith)
make sendfile() function (thanks @hodgestar)
fix silly uploading copy (thanks @hodgestar)
turn off buffering for Nginx to stream the response
include debug output in sendfile (thanks @hodgestar)
Merge branch 'feature/issue-867-export-raw-message-exports' into develop
Merge branch 'develop' of github.com:praekelt/vumi-go into develop