Presence improvements

[rjeczalik]

Hey @paddybyers,

during reading the Java's realtime Presence implementation I spotted two minor things I think either differ from the spec or possibly may be a bug.

• there's no overloaded Get method that takes connectionID for filtering the presence map (only for connectionID)
• presence.remove does not take timestamps into account like the put method

I might be wrong regarding the second, at least it looked suspicious to me.

┆Issue is synchronized with this Jira Task by Unito

[mattheworiordan]

@paddybyers do you believe this is still an issue? If so, I will add it to the backlog