[bug_1006722] Generate Event Stats for MP on a country level

This is part of the solution for [bug 1006722](https://bugzilla.mozilla.org/show_bug.cgi?id=1006722).

It generates statistics for events in the [webmaker events service](https://github.com/mozilla/webmaker-events-service) on a country by country level. This is needed in order to generate the heatmap [bug 1006722](https://bugzilla.mozilla.org/show_bug.cgi?id=1006722) refers to.

The heatmap has been created as a node module here: [fuzzyfox/makerparty-heatmap](https://github.com/fuzzyfox/makerparty-heatmap). Demo implementation can be [clearly seen here](https://github.com/fuzzyfox/makerparty/compare/event-stats...heatmap). The demo implements the heatmap ontop of the event-stats branch (this PR). New PR to be filed once this is merged (if makes sense to use heatmap in this manner)