Fix transfer-encoding: chunked issue with Safari

[cboulanger]

The server-side progress indicator implemented with chunked http responses doesn't work with Safari yet, which processes the http response only when the connection is closed. Need to investigate and find a workaround.

Possible solution:
http://stackoverflow.com/questions/24472818/chunked-transfer-in-chrome

[cboulanger]

It was fixed by adding a <br/> to the chunk.