Remove delimiter type constraint

[ForNeVeR]

After report by @alexreg in #14 that | doesn't work I decided to review the delimiter typing. I've found that things like \left) are actually supposed to work, so I removed the constraint on the delimiter type from the closing brace code.

That way, now things like \left| \frac{2}{2} \right| work, and even \left) \frac{2}{2} \right|.

[gsomix]

LGTM

[ForNeVeR]

Thanks for the review.

[alexreg]

Yep, I think this is the right way to go about things.