\slash not real LaTeX command, output as '/'

\slash isn't LaTeX, but '/' is: http://mathb.in/17532

Typing '/' results in LiveFraction, so need \slash so it's even possible
to type that character.

Also, not a delimiter so move out of the 'delimiters' section, to the
'various symbols' section.
\{open,close}curlybrace aren't LaTeX, use \{l,r}brace

http://mathb.in/17532

Keep \{open,close}curlybrace for backcompat
\caret and \underscore not real LaTeX commands

Can just use \_ for \underscore instead: http://mathb.in/17532

\caret is more annoying, settling for \text{^} (this is in
advancedSymbols.js anyway):
http://tex.stackexchange.com/questions/77646/how-to-typset-the-symbol-caret-circumflex-hat
Merge pull request #323 from mathquill/fix.symbols

Fix symbols LaTeX output