Auth, bug fixes

• Let users auth via an email again via gcs_auth
• correct file.copy behaviour in gcs_load_all() (#112) - thanks @jasonmhoule
• Allow GCS uploads if ACL has been set at bucket level (#111)
• Let users set the boundary between simple and resumable upload limit via new option option(googleCloudStorageR.upload_limit) or gcs_upload_set_limit() - default is 5000000L or 5MB (#120)
• Suppress warning for when resumable uploads are requesting the upload URL (#120)
• Fix ability to upload meta data with objects (#108)
• If file has no filesize will message without an error (#123)
• If project has no buckets will give NULL and not an error (#100)
• Fix gcs_save_all() to also accept bucket level ACL (#129)
• Fix listing buckets for projects gcs_list_buckets() (#100)
• Add gcs_setup() to help first time setup