Fix autoupdate issue

* Add -L option to curl calls to force following links redirection
* Isolate update function in a proper file:
  Updating a living script is not a really good idea. In some case
  bash will try to follow execution of the actual instance in the
  updated file, leading to errors or bad behavior.
Fix install script links
Merge pull request #10 from vannell/fix_auto_update

Fix autoupdate issue
Thanks for the pull request this is a better idea for updating and everything is working good.