v0.4.0

Major changes

• Update Bucket storageClass to include MULTI_REGIONAL, REGIONAL, and COLDLINE
• Fix bug where gcs_load wouldn't work if file name not ".RData"
• Add gcs_first and gcs_last to autosave your file workspace to GCS
• Better message feedback on file sizes
• Add gcs_save_all and gcs_load_all which will zip, save/load and upload/download a directory
• Add use of _gcssave.yaml file to control gcs_first/last behaviour
• Allow passing a bucket object to functions that expect a bucket name (#76)
• remove now unsupported travis environment argument