Minor correction in thanks message
DRYing conference and talk controllers
Some validations on conference model
Addedd http_accept_language middleware to be used with translations in
the future
Merge branch 'develop' of github.com:juanramb/gul-gultalks into juanramb-develop
Fixed some types.

- Some types were set to not null and it makes the app crash during adding talk process.
- Added more default values.