Add basic auto-render extension

Summary:
Add an auto-render extension to render math on a page. It
exposes a global function (maybe we should attach it to `katex`?) to
render math in an element. It comes with a README on how to use it.
Also, make `make build` build the minified file.

Fixes #26

Test Plan:
 - Visit http://localhost:7936/contrib/auto-render/
 - See that all of the math renders correctly
 - `make test`

Reviewers: alpert, kevinb

Reviewed By: kevinb

Differential Revision: https://phabricator.khanacademy.org/D16620

server.js

@@ -9,20 +9,33 @@ var app = express();
 
 app.use(express.logger());
 
-app.get("/katex.js", function(req, res, next) {
-    var b = browserify();
-    b.add("./katex");
+var serveBrowserified = function(file, standaloneName) {
+    return function(req, res, next) {
+        var b = browserify();
+        b.add(file);
 
-    var stream = b.bundle({standalone: "katex"});
+        var options = {};
+        if (standaloneName) {
+            options.standalone = standaloneName;
+        }
 
-    var body = "";
-    stream.on("data", function(s) { body += s; });
-    stream.on("error", function(e) { next(e); });
-    stream.on("end", function() {
-        res.setHeader("Content-Type", "text/javascript");
-        res.send(body);
-    });
-});
+        var stream = b.bundle(options);
+
+        var body = "";
+        stream.on("data", function(s) { body += s; });
+        stream.on("error", function(e) { next(e); });
+        stream.on("end", function() {
+            res.setHeader("Content-Type", "text/javascript");
+            res.send(body);
+        });
+    };
+};
+
+app.get("/katex.js", serveBrowserified("./katex", "katex"));
+app.get("/test/katex-spec.js", serveBrowserified("./test/katex-spec"));
+app.get("/contrib/auto-render/auto-render.js",
+        serveBrowserified("./contrib/auto-render/auto-render",
+                          "renderMathInElement"));
 
 app.get("/katex.css", function(req, res, next) {
     fs.readFile("static/katex.less", {encoding: "utf8"}, function(err, data) {
@@ -48,24 +61,10 @@ app.get("/katex.css", function(req, res, next) {
     });
 });
 
-app.get("/test/katex-spec.js", function(req, res, next) {
-    var b = browserify();
-    b.add("./test/katex-spec");
-
-    var stream = b.bundle({});
-
-    var body = "";
-    stream.on("data", function(s) { body += s; });
-    stream.on("error", function(e) { next(e); });
-    stream.on("end", function() {
-        res.setHeader("Content-Type", "text/javascript");
-        res.send(body);
-    });
-});
-
 app.use(express.static(path.join(__dirname, "static")));
 app.use(express.static(path.join(__dirname, "build")));
 app.use("/test", express.static(path.join(__dirname, "test")));
+app.use("/contrib", express.static(path.join(__dirname, "contrib")));
 
 app.use(function(err, req, res, next) {
     console.error(err.stack);