bootstrap to all templates n' validation improved

- Twitter Bootstrap was added to all the templates using Django Template
Inheritance.
- "base.html" template added as base of all templates.
- template files not used were removed.
- validate_url now returns string.
- tests for validate_url updated
- 'views.py' update to work with validate_url
- 'urls.py' and shortener improved (ENGLISH ADDED).

Now Everything is in ENGLISH!!!!