Project contributors list

**Short description**: Show the top x / a random set of x contributors on the homepage, each with profile picture and username (?)

**Location**: Homepage

**Why have this**: Give the project human faces; show that it's volunteer-based, and reward contributors with visibility.

**More info**:
* I'm not sure whether we should 'sort' contributors based on their number of contributions (which would be tricky, and extra work to come to a fair list), or simply display a random set of contributors. If random, we should probably set some kind of threshold per platform (e.g. 5 PRs or issues on GitHub; trust level 3 on the forum).
* The list should be pulled automatically from GitHub (the two repos; app & website), Transifex (or whatever translations tool we'll have) and the forum. What would be awesome, is if user matching would be done based on username, as to remove duplicates. If we sort based on contributions, people's effort on different platforms are added up (for them to appear higher on the list).
* I wonder if we should also add a 'The core team' page, listing manually selected key people. It'd also give room to list past contributors, such as the original creator and previous maintainers.