made hola an executable, changed to bundle template, added README, merged in dutch

Hi, When I went to use hola to test a patch to my rbenv-binstubs project, I noticed 'hola' was not installed as an executable. So I did it (plus a bit extra):
* made hola an executable in gemspec (so bundle --binstubs creates bin/hola)
* used bundle template (makes it simple to build and publish gem)
* made VERSION a class variable
* Added a README.md and LICENSE.txt file
* Added .travis.yml as an example for automated CI testing