Add x-gzip to cli supported mimetypes
Add x-gzip to cli supported mimetypes

On OS X application/g-zip comes back as application/x-gzip

Signed-off-by: Kris Hicks <6d3f751023bc04266d4da2ff94804f4240839fe2@pivotal.io>

pivotal-cf/cred-alert,pivotal-cf/cred-alert