Replace deprecated simplejson usage with std lib json module.
Add _make_url_* separate functions for generate urls for newsletter app.
Replace some repeated url generation with new _make_url* functions.
Code style cleaning on newsletter/views.py
Replace obsolete usage of STATIC_URL variable with static template tag ...

... on web/home.html template.
Minor code cleaning on web/views.py
Merge pull request #31 from python-spain/minor-improvements

Minor improvements