Parses a hash string of the format `'{ :a => "something" }'` into an actual ruby hash object `{ a: "something" }`. This is useful when you by mistake serialize hashes and save it in database column or a text file and you want to convert them back to hashes without the security issues of executing `eval(hash_string)`. By default only following classes are allowed to be deserialized: * TrueClass * FalseClass * NilClass * Numeric * String * Array * Hash A HashParser::BadHash exception is thrown if unserializable values are present.