add more of api

tests/simple.js

@@ -6,19 +6,46 @@ var lat = 40.2574448;
 var lng = -111.7089464;
 var level = 15;
 
+
+
+//
+// Convert from Lat / Lng
+//
 var key = S2.latLngToKey(lat, lng, level);
-// '4/032212303102210'
 console.log(key);
+// '4/032212303102210'
 
+
+
+//
+// Convert between Hilbert Curve Quadtree Key and S2 Cell Id
+//
 var id = S2.keyToId(key);
-// '9749618446378729472'
 console.log(id);
+// '9749618446378729472'
 
+var key = S2.idToKey(id);
+console.log(key);
+// '9749618446378729472'
+
+
+
+//
+// Neighbors
+//
 var neighbors = S2.latLngToNeighborKeys(lat, lng, level);
-// [ keyLeft, keyDown, keyRight, keyUp ]
 console.log(neighbors);
+// [ keyLeft, keyDown, keyRight, keyUp ]
 
+
+
+//
+// Previous, Next, and Step
+//
 var nextKey = S2.nextKey(key);
 console.log(nextKey);
 var prevKey = S2.prevKey(key);
 console.log(prevKey);
+
+var backTenKeys = S2.stepKey(key, -10);
+console.log(backTenKeys);