Start of preventing users from interacting with messages when they are not in the room.

Improvements/reactions

LingoHub Update 

Manual push by LingoHub User: Gabriel Engel.
Project: Rocket.Chat

Made with  by https://lingohub.com

Add role field to user creation form

Closes https://github.com/RocketChat/Rocket.Chat/issues/3262

Prevent someone from reacting if they are muted

Created guest user permission

Make the sidebar movement transition faster

Do not close request window by mistake

It feels laggy right now, this improves the perceived speed when clicking "More channels", "Add channel", etc.

Make emoji search perform across all categories

Fix text clipping in spotlight input

Fixes #1533

fix URL for cordova when quoting a message

fix docs links

Simplify travis.yml

Move CONTRIBUTING.md to .github directory

Restore comma as Spanish speakers have corrected me

Remove extraneous comma in "no longer moderator, by <user>" message

`sudo: false` is not longer required to make use of the container-based infrastructure.