Update version to 1.2.15

Merge pull request #95 from liaoyunify/master

modify version

Merge pull request #90 from yunify/qingstor_snapshot

support to specify backstore_type for snapshot

Update version to 1.2.11

Update version to 1.2.10

Update version to 1.2.9

Update version to 1.2.8

Merge pull request #63 from yunify/add_InstanceGroupsAction

Add InstanceGroupsAction

Update version to 1.2.5

Update version to 1.2.4