Related to #1359. Removing extra $ that older versions sympy add.

Older versions of sympy put in an extra $ when using
latex(e, mode='plain'). We are removing those before we add our
own to make sure it works.

IPython/extensions/sympyprinting.py

@@ -60,6 +60,7 b' def print_latex(o):'
     """A function to generate the latex representation of sympy expressions."""
     s = latex(o, mode='plain')
     s = s.replace('\\dag','\\dagger')
+    s = s.strip('$')
     return '$$%s$$' % s