Respect LaTeX Foreign Characters

In the LaTeX commands [here](http://en.wikibooks.org/wiki/LaTeX/Special_Characters#Escaped_codes), `\"` and `` \` `` are used.  Currently, Smartparens will match `"` and `` ` `` in these circumstances (the previous character is a backslash).  I would have a pull request, but I committed https://github.com/Sammidysam/smartparens/commit/29e955741a51d13774ee37154235e28bcd6878d6 on my fork and it did not work.  Functionality should be added so that pressing `"` will come out as `"` when a backslash is the previous character and `` ` `` `` ` `` in the same circumstance.