0.1.6, update changelog, readme, plugins list

plugins/exec/README.md

@@ -0,0 +1,15 @@
+# Exec Plugin
+
+The exec plugin can execute arbitrary commands which return flattened
+JSON.
+
+For example, if you have a json-returning command called mycollector, you could
+setup the exec plugin with:
+
+```
+[[exec.commands]]
+command = "/usr/bin/mycollector --output=json"
+name = "mycollector"
+```
+
+The name is used as a prefix for the measurements.