Detect current place timeout on startup

[goatgoose]

Currently, the placed timestamp is initially set to 0 for each user:

PlaceBot/place_bot/user.py

Line 28 in db14637

self.placed_timestamp = 0

However, if the owner of the user isn't keeping track of their reddit account's current timeout, this could lead to problems. Instead, the current timeout value should be queried via the hot-potato API, and set here instead.