Modified bin/shoes script to run from everywhere

* it also uses bin/ruby-shoes so that the require/execute logic
  is not duplicated :-)
Now with a basic implementation of readlink -f for mac inside (so it works there)
adjusted 2 samples so they are independent of where they are run from
Use exec instead of eval
Merge pull request #450 from PragTob/binshoesFromEverywhere

Modified bin/shoes script to run from everywhere