The conversations index page can get overwhelming after you've had a lot of contact with folks. I'd like a way to make it easier to follow a few important threads without getting bogged down by the rest.
A PR addressing this issue should: 
• Add an Archive button to every conversation
• When clicked, remove the conversation from /conversations
• If any conversations are archived, add a link to the bottom labeled "Archived conversations"
• When clicking this link, visit /conversations/archived and show the archived ones
• Each conversation on this screen should have a Unarchive button that moves it back to /conversations