We use only mysql, so updating this means a lot of unused db backends
like sqlite do not need to be built with gyp anymore.
Note that this version is not yet released as stable, but works fine for
us. The outstanding issues are not related to our use-case from what I
can tell.
Fixes#82
The initial idea was to store exactly where the backups are stored.
But this only causes problems for migrations where the bucket might
change and clones where the prefix (box.id) changes.
Thus, it's best to leave the url creation to the caas side. (That
has to be done in another change)