New "browse" UI

Also, separated out browse, ?meta, and ?module request handlers.

Fixes #82

modules/__tests__/legacyURLs-test.js

@@ -27,4 +27,14 @@ describe('Legacy URLs', () => {
         done();
       });
   });
+
+  it('redirect */ to /browse/*/', done => {
+    request(server)
+      .get('/react@16.8.0/umd/')
+      .end((err, res) => {
+        expect(res.statusCode).toBe(302);
+        expect(res.headers.location).toEqual('/browse/react@16.8.0/umd/');
+        done();
+      });
+  });
 });