Add more symbols

Summary:
', \angle, \circ, \gets, \infty, \leftarrow, \prime, \rightarrow, \times, \to

Fixes T1191.

Reviewers: emily

Reviewed By: emily

Maniphest Tasks: T1191

Differential Revision: http://phabricator.khanacademy.org/D3053

katex.js

@@ -151,19 +151,28 @@ var charLookup = {
     "*": "\u2217",
     "-": "\u2212",
     "`": "\u2018",
-    "\\cdot": "\u22C5",
-    "\\lvert": "|",
-    "\\rvert": "|",
-    "\\pm": "\u00b1",
-    "\\div": "\u00f7",
-    "\\leq": "\u2264",
-    "\\geq": "\u2265",
-    "\\neq": "\u2260",
-    "\\nleq": "\u2270",
-    "\\ngeq": "\u2271",
     "\\ ": "\u00a0",
+    "\\angle": "\u2220",
+    "\\cdot": "\u22c5",
+    "\\circ": "\u2218",
+    "\\colon": ":",
+    "\\div": "\u00f7",
+    "\\geq": "\u2265",
+    "\\gets": "\u2190",
+    "\\infty": "\u221e",
+    "\\leftarrow": "\u2190",
+    "\\leq": "\u2264",
+    "\\lvert": "|",
+    "\\neq": "\u2260",
+    "\\ngeq": "\u2271",
+    "\\nleq": "\u2270",
+    "\\pm": "\u00b1",
+    "\\prime": "\u2032",
+    "\\rightarrow": "\u2192",
+    "\\rvert": "|",
     "\\space": "\u00a0",
-    "\\colon": ":"
+    "\\times": "\u00d7",
+    "\\to": "\u2192"
 };
 
 var textit = function(value) {