Soil - moisture (#418)

* updated servo calibrator

* updated plot analog pin example

* updated servo example

* first drop of soil moisture

* updated picture

* fixing macros

* update code section

* 5 seconds

* adding soil moisture

* fixing links

docs/projects/soil-moisture.md

@@ -0,0 +1,28 @@
+# Soil Moisture
+
+
+### ~avatar avatar
+
+Make a funny milky-monster robot!
+
+### ~
+
+![](/static/mb/projects/soil-moisture/soil-moisture.jpg)
+
+## Materials
+
+* 1 @boardname@ with battery pack and batteries
+* 2 long nails or silver
+* 2 crocodile clips
+
+## Activities
+
+* [Make](/projects/soil-moisture/make)  
+* [Code](/projects/soil-moisture/code)
+* [Connect](/projects/soil-moisture/connect)
+
+### ~button /projects/soil-moisture/make
+
+Let's get started!
+
+### ~