Opens message links popup menu

[shreyamalviya]

As of now, this does the following:

• Opens menu with links on pressing v
• Narrows to a stream (but does nothing if not subscribed to stream)
• Narrows to PM with a user (has an issue for users with whom no previous private conversation has taken place)

Final functionality includes:
Pressing enter on one of the buttons in the links popup menu does one of the following, depending on the link:
* narrow to stream
* narrow to user
* open image in system's default viewer
* open link in system's default browser

[amanagr]

How about:

        with requests.get(url,
                          auth=requests.auth.HTTPBasicAuth(client.email,
                                                          client.api_key),
                          stream=True) as r:

where client is controller.client.

[shreyamalviya]

That works. Thanks a lot, @amanagr!

[zulipbot]

Heads up @shreyamalviya, we just merged some commits that conflict with the changes your made in this pull request! You can review this repository's recent commits to see where the conflicts occur. Please rebase your feature branch against the upstream/master branch and resolve your pull request's merge conflicts accordingly.

[neiljp]

@shreyamalviya Thanks for your initial work on this 👍 I'm going to close this now since we have a menu structure in place and PRs open for the remaining features (open in web-browser #698, open downloadable media #740).

If there were other features which you believe were in this PR and are not integrated, in those PRs, we'd appreciate if you were able to file an issue or mention it briefly on #zulip-terminal - thanks!