Changed corners to work based on declared margin

lib/data/players.js

@@ -1,13 +1,13 @@
 GridGame.data.players = [
   {
     name: 'green',
-    start: GridGame.positions.north_west_corner,
+    start: GridGame.positions.north_west_corner(2),
     direction: 'east',
     playable: true
   },
   {
     name: 'red',
-    start: GridGame.positions.south_east_corner,
+    start: GridGame.positions.south_east_corner(2),
     direction: 'west',
     playable: true
   }

lib/positions.js

@@ -1,22 +1,32 @@
 GridGame.positions = {
-  north_west_corner: {
-    x: 2,
-    y: 2
+  north_west_corner: function (margin) {
+    return {
+      x: margin,
+      y: margin
+    }
   },
-  north_east_corner: {
-    x: (GridGame.data.game.width - 3),
-    y: 2
+  north_east_corner: function (margin) {
+    return {
+      x: (GridGame.data.game.width - margin - 1),
+      y: margin
+    }
   },
-  south_west_corner: {
-    x: 2,
-    y: (GridGame.data.game.height - 3)
+  south_west_corner: function (margin) {
+    return {
+      x: margin,
+      y: (GridGame.data.game.height - margin - 1)
+    }
   },
-  south_east_corner: {
-    x: (GridGame.data.game.width - 3),
-    y: (GridGame.data.game.height - 3)
+  south_east_corner: function (margin) {
+    return {
+      x: (GridGame.data.game.width - margin - 1),
+      y: (GridGame.data.game.height - margin - 1)
+    }
   },
-  center: {
-    x: Math.floor(GridGame.data.game.width / 2),
-    y: Math.floor(GridGame.data.game.height / 2)
+  center: function () {
+    return {
+      x: Math.floor(GridGame.data.game.width / 2),
+      y: Math.floor(GridGame.data.game.height / 2)
+    }
   }
 };