handling parentheses inside strings at the repl

[glycerine]

At the repl

> (def b ")")
>>

will cause glisp to hang because it doesn't actually parse the input, just check that the parenthesis balance. I fixed this in zygomys as of https://github.com/glycerine/zygomys/commit/01562f6161e20b70040704f1c805e3e64af4ede7 if you wish to backport.