since it no longer is mirror_dir but `work_dir`
for status.json and custom-mirrors.json

changed constants internal
added deleting in httpfh.update_mirrors()

setting pacman-mirrors.conf dynamically (reverted from commit e0a94c0d)

Since travis builds are prone to fail if pacman-mirrors.conf is not found
 It has been made possible to change location by adding it to internal config
 It can then be changed on-the-fly to fit travis build (reverted from commit 9e9f32d5)

Since travis builds are prone to fail if pacman-mirrors.conf is not found
 It has been made possible to change location by adding it to internal config
 It can then be changed on-the-fly to fit travis build