Removed the unused setting 'session.payload'.

Signed-off-by: Isern Palaus <ipalaus@ipalaus.es>
Merge pull request #1999 from ipalaus/fix/session-payload

Removed the unused setting 'session.payload'.
Added sendmail path config option.
Updated available drivers for mail.
Merge branch 'develop' of github.com:laravel/laravel into develop
update dependencies