Update located servers when a lemma is registered or unteregistered

@dougbradbury @evanShap 
There's quite a few changes on this PR
- Method same? removed from LocatedServers: Now it uses method in super-class which just uses the name to identify if it's the same 
- variable last_modified on ReapableRepository was not being modified (now using attr_accessor)
- Remove lema from GrabbedLemas when firing player (otherwise last_modified is not been updated)
- Redefine reap for LocatedServers: this uses the last_modified to see if there was any modification on the server on the last 3 seconds (beacon messages are received every 2 secs). Last_modified is loaded from the grabbedLemmas.last_modified field, which is updated every time a new lemma is added or removed. There's a point to be made here. When a new server is added, LocatedServers is updated b/c the server beacon message calls remember_server (line 28 on UdpListener). If the Server is turned off, no message is sent and therefore the server will be hooked (and the lemmas would still appear on teh other guests list)