Common Lisp: add modern utility libraries

[tre-flip]

Common Lisp has evolved since it was standardized. Many great ideas weren't popular during the standardization process and many useful features didn't make it into the standard. However, hackers have written many good utility libraries since then to cater the demand for these features. I think it would be nice to allow the use of libraries like Alexandria or Serapeum (and probably others) which are used in countless applications and represent modern Common Lisp style.

[hobovsky]

Requests for new libraries should be posted to codewars/runner repository.

[tre-flip]

Moved to codewars/runner repository.