Adds math commands, HTML rendering, and screenshotter tests.

This is part 2 of 3.  Part 1 added new fonts metrics.  Part 2 will add MathML support and unit tests.

src/symbols.js

@@ -2514,6 +2514,17 @@ var symbols = {
             font: "main",
             group: "accent",
             replace: "\u02d9"
+        },
+
+        "\\imath": {
+            font: "main",
+            group: "mathord",
+            replace: "\u0131"
+        },
+        "\\jmath": {
+            font: "main",
+            group: "mathord",
+            replace: "\u0237"
         }
     },
     "text": {