Stalk friends in Mensa

[adideshp]

Possible subtasks:

• [x] Display all the users in Mensa.
• [x] Option to add/ remove a friend from friends list.
• [x] Sending "IN MENSA" msg when a user enters the Mensa building.
• [x] Sending "OUT MENSA" msg when leaving the Mensa building.

[vivek-sethia]

Refer #44 for 'Display all users in Mensa'

[vivek-sethia]

Refer #47