Issue #44: Streaming Response

[xtzhang1122]

This PR aims to address Issue #44 , which would allow parts of the response to be received and processed as they are ready.

[swaptr]

Only /conversation endpoint is supposed to send streamed response. All others should be standard HTTP responses.

[swaptr]

Please fix the PR using this information.
/conversations: to fetch all user conversations
/conversation/{id}: fetch single user conversation history
/conversation: the streaming conversation endpoint for the system