Compile and test MongooseIM with Erlang/OTP 20

Twnel Rooms support for Release 2.1.0

support after qs for messages api

Release 2.1.0

Update version and changelog for beta2

add company field to groups

bump version to 2.1.0beta1

Merge pull request esl#1164 from esl/rel-2.0

MongooseIM 2.0.1

Merge pull request esl#1069 from esl/rel-2.0

MongooseIM 2.0.0

[skip ci] Cluster management considerations (esl#897)