replace deprecated sb-ext:quit with sb-ext:exit

As of 1.0.57[1]

[1]: http://sbcl.org/all-news.html#1.0.57
Merge pull request #53 from PuercoPop/patch-1

replace deprecated sb-ext:quit with sb-ext:exit
current-directory not needed, use uiop instead

   Add setf expansion for getcwd
Make tags indices URL absolute
More robust directory changing

     - Doesn't fail when the directory is missing a trailing '/'
     - When directory doesn't exist it signals an informative
       condition.
Merge pull request #56 from PuercoPop/misc-fixes

Misc fixes
Fix validation errors.
Merge pull request #59 from Ferada/validation-fixes

Fix validation errors.
Merge branch 'master' into basic-deploy