Remove room renew

[scottinet]

⚠️ depends on #259 ⚠️

• Simplify needlessly complicated Room object workflow by:
  • getting rid of the renew method (documentation update incoming shortly)
  • regrouping the active and subscribing state flags into an unique roomstate state machine
  • answering with errors and letting users control their workflow instead of trying to resolve problems they might not have in the first place
• remove the unused options argument from Room.unsubscribe
• fix event leaks occuring after multiple subscribes
• fix https://github.com/kuzzleio/kuzzle-sdk/issues/53

[codecov-io]

Codecov Report

Merging #260 into 6.x will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              6.x     #260      +/-   ##
==========================================
- Coverage   98.27%   98.25%   -0.02%     
==========================================
  Files          17       17              
  Lines        2142     2125      -17     
  Branches      620      618       -2     
==========================================
- Hits         2105     2088      -17     
  Misses         37       37

Impacted Files	Coverage Δ
src/Room.js	100% <100%> (ø)	⬆️
src/networkWrapper/protocols/abstract/realtime.js	98.63% <100%> (ø)	⬆️
src/Kuzzle.js	97.46% <100%> (+0.01%)	⬆️

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[ballinette]

nitpicking: what do we do if the client still receive notifications while beeing inactive (I guess it shouldn't, but...) ?
I suggest, in notify method, to emit the notification only if this.roomstate === 'active' (and at least log a warning message if not)

[scottinet]

@ballinette > this should not happen, as the room is marked inactive after a network disconnection or after an authentication token has expired. In both these cases, Kuzzle will automatically remove the subscription and stop notifying that connection.

I suggest to leave it like that: either it works as I think it will, or it does not and issues will be written, allowing us to detect a potential room management problem, probably on Kuzzle's side.