Add Redis cache backend: used for sessions

See vosae-app: https://github.com/Naeka/vosae-app/commit/3666036c351be761042f52b23a28f224118c7668

Signed-off-by: Maxime Gaillard <maxime@naeka.fr>
Errors are now handled in ember and ember-data
Remove raven in debug mode
Merge branch 'release/2014-02.1'