Sync styles with khan-exercises

Summary:
Get the styles into a form that they can be directly copied over to
khan-exercises, with no changes. Mostly just changing #math to .mathmathmath
and adding a font style and size.

Test Plan: Make sure that the local test still works.

Reviewers: spicyj

Reviewed By: spicyj

Differential Revision: http://phabricator.benalpert.com/D47

static/main.css

@@ -0,0 +1,9 @@
+body {
+    margin: 0px;
+    padding: 0px;
+}
+
+input {
+    margin: 0px;
+    font-size: 100%;
+}