Add some AMS characters

Summary:
\nleq and \ngeq are AMS characters, so add support for parsing and
showing those. Also, add font metrics from the ams_regular font.

Test Plan:
View `\ngeq \geq`, make sure that they look the same but with a
slash through `\ngeq`. View `a \ngeq b`, make sure there's the right spacing
for a rel.

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D3547

Parser.js

@@ -265,11 +265,13 @@ var copyFuncs = {
         "\\leftarrow",
         "\\leq",
         "\\neq",
-        "\\ngeq",
-        "\\nleq",
         "\\rightarrow",
         "\\to"
     ],
+    "amsrel": [
+        "\\ngeq",
+        "\\nleq"
+    ],
     "spacing": [
         "\\ ",
         "\\,",

buildTree.js

@@ -40,6 +40,7 @@ var groupToType = {
     textord: "mord",
     bin: "mbin",
     rel: "mrel",
+    amsrel: "mrel",
     open: "mopen",
     close: "mclose",
     frac: "minner",
@@ -90,6 +91,10 @@ var groupTypes = {
         return makeSpan(["mrel", options.color], [mathrm(group.value)]);
     },
 
+    amsrel: function(group, options, prev) {
+        return makeSpan(["mrel", options.color], [amsrm(group.value)]);
+    },
+
     supsub: function(group, options, prev) {
         var base = buildGroup(group.value.base, options.reset());
 
@@ -467,6 +472,10 @@ var mathrm = function(value) {
     return makeText(value, "main-regular");
 };
 
+var amsrm = function(value) {
+    return makeSpan(["amsrm"], [makeText(value, "ams-regular")]);
+};
+
 var buildTree = function(tree) {
     // Setup the default options
     var options = new Options(Style.TEXT, "");

metric_parse.rb

@@ -39,7 +39,7 @@ end
 font_dir = File.join(File.dirname(__FILE__), 'static/fonts/')
 metrics = {}
 
-%w[main-regular math-italic].each do |face|
+%w[main-regular math-italic ams-regular].each do |face|
   metrics[face] = metrics_for_file(File.join(font_dir, 'katex_%s.ttf' % face))
 end
 

static/katex.less

@@ -30,6 +30,10 @@ big parens
         font-style: italic;
     }
 
+    .amsrm {
+        font-family: katex_ams;
+    }
+
     @thinspace: 0.16667em;
     @mediumspace: 0.22222em;
     @thickspace: 0.27778em;