bug: empty string can no longer be parsed

[erkkikeranen]

• [ ] make sure "" can be parsed by the reader
• [ ] add unit test

clojure.core=> ""
#Condition["Reader Error: could not read next form; Error(("\"\"", Tag))"]

[Tko1]

Bug on Feature/value regex, to be fixed before merging

(Let me know if it has shown up anywhere else, although I don't believe it would be)