Added jquery as external dependency.

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "external/mathjax"]
 	path = external/mathjax
 	url = http://github.com/mathjax/MathJax
+[submodule "external/jquery"]
+	path = external/jquery
+	url = https://github.com/jquery/jquery.git

external/jquery

@@ -0,0 +1 @@
+Subproject commit e529d91ccd00a75fcfa45a6aebaf8ecf0a9bac4b