getting rid of now-unnecessary demo file

math-replay/mathjax-demo.haml

@@ -1,9 +0,0 @@
-%html
-  %head
-    %script{:type => "text/x-mathjax-config"}
-      MathJax.Hub.Config({tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']]}});
-    %script{:type => "text/javascript", :src => "http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"}
-  %body
-    %p
-      When $a \ne 0$, there are two solutions to \(ax^2 + bx + c = 0\)
-      and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$