Update README.md

[Coffee2CodeNL]

Added Gitter.im chat for support.

As discussed in #5394

[akarnokd]

Why regrouping? Actually I prefer StackOverflow because questions can be isolated much better. The gitter channels usually invoke chaos by talking over each other and hard to follow who reacted to what.

[Coffee2CodeNL]

Realtime -> "Slightly Slower" communication -> Social Media was my idea.
Unless you want it sorted by preferred communication channels, then i'll update it to your liking.

[akarnokd]

Please add this to the bottom without changing the order of the existing list elements.

[codecov]

Codecov Report

Merging #5395 into 2.x will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##               2.x    #5395      +/-   ##
===========================================
- Coverage     96.2%   96.15%   -0.06%     
- Complexity    5784     5785       +1     
===========================================
  Files          630      630              
  Lines        41197    41197              
  Branches      5728     5728              
===========================================
- Hits         39635    39614      -21     
- Misses         607      623      +16     
- Partials       955      960       +5

Impacted Files	Coverage Δ	Complexity Δ
...ava/io/reactivex/processors/BehaviorProcessor.java	87.61% <0%> (-4.87%)	61% <0%> (ø)
...in/java/io/reactivex/subjects/BehaviorSubject.java	85.93% <0%> (-4.69%)	56% <0%> (ø)
.../internal/operators/maybe/MaybeTakeUntilMaybe.java	95.91% <0%> (-4.09%)	2% <0%> (ø)
...ex/internal/operators/maybe/MaybeTimeoutMaybe.java	95.58% <0%> (-2.95%)	2% <0%> (ø)
...x/internal/operators/maybe/MaybeSwitchIfEmpty.java	97.22% <0%> (-2.78%)	2% <0%> (ø)
...main/java/io/reactivex/subjects/SingleSubject.java	97.61% <0%> (-2.39%)	39% <0%> (-1%)
...l/operators/observable/ObservableFlatMapMaybe.java	89.54% <0%> (-1.97%)	2% <0%> (ø)
.../io/reactivex/disposables/CompositeDisposable.java	97.24% <0%> (-1.84%)	39% <0%> (-1%)
...nal/operators/flowable/FlowableConcatMapEager.java	96.53% <0%> (-1.74%)	2% <0%> (ø)
...nternal/operators/observable/ObservableCreate.java	97.43% <0%> (-1.71%)	2% <0%> (ø)
... and 36 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8a62afb...2e3ddb5. Read the comment docs.