show error message when db connection test failed
Tweak variable and styling based on #146.

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch '2.1'

Signed-off-by: crynobone <crynobone@gmail.com>

Conflicts:
	src/Orchestra/Foundation/Installation/Requirement.php
	src/views/install/index/_database.blade.php