Address a few issues

[displague]

Addresses a few issues

• Remove the linode-region option, redundant to linode-label (Closes Must provide a region or a Linode ID #24)
• Don't delete volumes on volume rm (Closes Remove docker volume without removing the physical volume #23)
  • Add volume create option to delete Linode volumes on volume rm
• Support BTRFS, XFS, EXT(2,3,4) (Closes Add ability to specify filesystem type #7)

[displague]

By fetching the region from the instance, instead of taking it as a user parameter, we also avoid the potential issue of a user supplied region being an alias region, which the volume list filter-by-region poll would never resolve:

docker-volume-linode/driver.go

Line 391 in be8f94b

if jsonFilter, err = json.Marshal(map[string]string{"label": volumeLabel, "region": driver.region}); err != nil {

I encountered this a few times when using us-south which is an alias for us-central (Dallas, TX).