delete slots from frames
ConsumeThreeOctalDigits works in ParseWord and ParseList
accept backslash:n,r,t
test backslash escaping
fixed parse_test T3
Merge pull request #5 from MrWerewolf/master

Recursive descent parsing for expr
Merge https://github.com/tcca/goterp
TODO Garbage Producers
Concatenate expr command arguments before evaluating.