Home: People invite UI fix

This branch fixes two issues:
It used to be that there were no limits on the number of people an user can invite. After this fix, the user be limited to inviting to up to 5 people. She/he will see the message "To keep the conversation close and meaningful, you can invite up to 5 people." displayed as the place holder text for the search box.
Question for @psybuzz, are users added based on the data-id that's in the DOM? I'm thinking of a senario when an user adds a person, but then removes the user from the selected list, is the person still added to the convo?

The second issue is that duplicate names are displayed when the user search for people. When a user selected a name, say 'Charles X', as one of the invitees, a subsequent search for 'Charles' will still show 'Charles X' in the dropdown of names. This push fixes that. Now the name is removed from the search results.
Ahhh........  when it comes time to merge this in, there may be a **merge conflict around here**.  In the mailman PR, I took these 3 lines out of the .click() handler, and replaced it with an .on() that comes afterwards.  Let me know if this gives you trouble down the road.