Rename "roles" to "units". Put units in their own folders.

lib/units/storage/plugins/image/param/gravity.js

@@ -0,0 +1,21 @@
+var GRAVITY = {
+  northwest: 'NorthWest'
+, north: 'North'
+, northeast: 'NorthEast'
+, west: 'West'
+, center: 'Center'
+, east: 'East'
+, southwest: 'SouthWest'
+, south: 'South'
+, southeast: 'SouthEast'
+}
+
+module.exports = function(raw) {
+  var parsed
+
+  if (raw && (parsed = GRAVITY[raw])) {
+    return parsed
+  }
+
+  return null
+}