Improve Contribution guide
The current version of the contribution guide should be updated to clearly communicate all the ways of how people can contribute to the project and what channels they can use in case of issues. There are some issues that were created in the tracker, instead of being asked in Gitter. For example: #343 (closed), #345 (closed), #346 (closed), #322 (closed), #363 (closed).
Also we need to change the naming of the guide to uppercase as it doesn't properly displayed for non-registered users:
This issue can be a good starting point to think on proper formatting and dividing to sections of the contribution guide as it includes too much of info that is hard to read on the first glance.