Updates for the rename of the `HTML` facade.

See laravel/framework#1231
Merge pull request #1973 from bencorlett/patch-3

Updates for the rename of the `HTML` facade.
Move slash redirects to application level.
Use app_path in global file. Closes #1975.
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.
merged