Fix broken auto-complete after function slime-fontify-string was renamed in slime.

For reference see:
https://github.com/slime/slime/search?utf8=%E2%9C%93&q=slime-fontify-string
Add support for multiple versions of slime.
Merge pull request #2 from josteink/master

Fix broken auto-complete after function slime-fontify-string was renamed...