Adds MathML support for math font commands.

This is part 3 or 3.  The first two pull requests added font metrics, HTML rendering, and screenshot tests.

src/buildTree.js

@@ -1,15 +1,30 @@
-
 var buildHTML = require("./buildHTML");
 var buildMathML = require("./buildMathML");
 var buildCommon = require("./buildCommon");
+var Options = require("./Options");
+var Settings = require("./Settings");
+var Style = require("./Style");
 
 var makeSpan = buildCommon.makeSpan;
 
 var buildTree = function(tree, expression, settings) {
+    settings = settings || new Settings({});
+
+    var startStyle = Style.TEXT;
+    if (settings.displayMode) {
+        startStyle = Style.DISPLAY;
+    }
+
+    // Setup the default options
+    var options = new Options({
+        style: startStyle,
+        size: "size5"
+    });
+
     // `buildHTML` sometimes messes with the parse tree (like turning bins ->
     // ords), so we build the MathML version first.
-    var mathMLNode = buildMathML(tree, expression, settings);
-    var htmlNode = buildHTML(tree, settings);
+    var mathMLNode = buildMathML(tree, expression, options);
+    var htmlNode = buildHTML(tree, options);
 
     var katexNode = makeSpan(["katex"], [
         mathMLNode, htmlNode