+ finish command implementations 
= finish unit tests
  Only a few left, to test the SORT command's edge cases (e.g. BY pattern)
+ determine if we should not use bool return values and instead throw redis_error. (latter).
+ maybe more fine-grained exceptions (not just redis_error but operation_not_permitted_error, etc.)
- benchmarking
- consistent hashing?
- make all string literals constants so they can be easily changed (minor)
- add conveniences that store a std::set in its entirety (same for std::list, std::vector)