github pages has to be on github.io

Github might have jumped the gun, but this looks to break April 15th 2021. user.github.com has to be user.github.io now.

Issue described here. 
https://github.blog/changelog/2021-01-29-github-pages-will-stop-redirecting-pages-sites-from-github-com-after-april-15-2021/

I'm doing this straight on github.com, feel free to ignore this PR and recreate it yourself.

install.sh

@@ -48,7 +48,7 @@ fi
 
 if [ "$JABBA_VERSION" == "latest" ]; then
     # resolving "latest" to an actual tag
-    JABBA_VERSION=$($JABBA_GET https://shyiko.github.com/jabba/latest)
+    JABBA_VERSION=$($JABBA_GET https://shyiko.github.io/jabba/latest)
 fi
 
 # http://semver.org/spec/v2.0.0.html