micro:coin activity (#650)

* microcoincode

* adding links

* fix file name

* a bit more docs

* Some minor edits

* Add a crypto blurb

* missing radio package

* updated info

* link to wallet activity

docs/SUMMARY.md

@@ -27,6 +27,7 @@
     * [Infection](/projects/infection)
     * [Fireflies](/projects/fireflies)
     * [Rock Paper Scissors Teams](/projects/rps-teams)
+    * [micro:coin](/projects/micro-coin)
     * [Inchworm](/projects/inchworm)
     * [Milk Carton Robot](/projects/milk-carton-robot)
     * [Milk monster](/projects/milky-monster)