added support for \over

changed stopType (string) parameter to breakOnInfix (boolean)
renamed rewriteInfixNodes to handleInfixNodes

added a test for {1 \over 2} \over 3, fixed some grammar, and added code in the parser to squash superfluous ordgroups

removed squashOrdGroups and instead don't create an "ordgroup" if one already exists

removed unnecessary variable

moved variable declarations out of "if" statements
removed comment

Fixed style issue with where variables are declared and remove unnecessary comment from functions.js
Merge pull request #101 from kevinb7/over

added support for \over
Adds new symbols.