Add recipes/sly

SLY is a fork of SLIME. SLY lives at https://github.com/capitaomorte/sly, SLIME lives at https://github.com/slime/slime.

A user asked me to support MELPA, see issue https://github.com/capitaomorte/sly/issues/12

Here's what I did testing-wise in emacs 24.3.1 
```
$ make recipes/sly
$ emacs -Q -f package-initialize --eval "(package-install-file \"$PWD/packages/sly-20140911.132.tar\")"
M-x sly   ;; you need to have a `lisp` executable, otherwise try C-u M-x sly
```