Version 0.1.2 release

In this release

• Add xarray from delayed methods in rhg_compute_tools.xarray (:issue:12)
• rhg_compute_tools.gcs.cp_to_gcs now calls gsutil in a subprocess instead of google.storage operations. This dramatically improves performance when transferring large numbers of small files (:issue:11)
• Additional cluster creation helpers in rhg_compute_tools.kubernetes (:issue:3)