Fix our getTypeOfGroup function

Add in the missing `'sizing'` entry, put the `'text'` entry in the correct
place, and replace `groupToType.ord` (a null value) with `groupToType.mathord`
(something real).

Test Plan:
 - See that `^3+` now puts the correct space before the `+`
 - See the new huxley test works, and nothing else has changed

Auditors: alpert

buildTree.js

@@ -47,7 +47,7 @@ var groupToType = {
     textord: "mord",
     bin: "mbin",
     rel: "mrel",
-    amsrel: "mrel",
+    text: "mord",
     open: "mopen",
     close: "mclose",
     frac: "minner",
@@ -55,20 +55,21 @@ var groupToType = {
     punct: "mpunct",
     ordgroup: "mord",
     namedfn: "mop",
-    katex: "mord",
-    text: "mord",
+    katex: "mord"
 };
 
 var getTypeOfGroup = function(group) {
     if (group == null) {
         // Like when typesetting $^3$
-        return groupToType.ord;
+        return groupToType.mathord;
     } else if (group.type === "supsub") {
         return getTypeOfGroup(group.value.base);
     } else if (group.type === "llap" || group.type === "rlap") {
         return getTypeOfGroup(group.value);
     } else if (group.type === "color") {
         return getTypeOfGroup(group.value.value);
+    } else if (group.type === "sizing") {
+        return getTypeOfGroup(group.value.value);
     } else {
         return groupToType[group.type];
     }

test/huxley/Huxleyfile

@@ -20,7 +20,7 @@ url=http://localhost:7936/test/huxley/test.html?m=\alpha\beta\gamma\omega
 url=http://localhost:7936/test/huxley/test.html?m=a+b-c\cdot d/e
 
 [Spacing]
-url=http://localhost:7936/test/huxley/test.html?m=[-1][1-1]1%%3D1(%%3D1)\lvert a\rvert~b
+url=http://localhost:7936/test/huxley/test.html?m=^3+[-1][1-1]1%%3D1(%%3D1)\lvert a\rvert~b
 
 [Functions]
 url=http://localhost:7936/test/huxley/test.html?m=\sin\cos\tan\ln\log