Make use of #persisted? method

In many places we were checking for identity which was the shorthand for
checking if the resource had been saved by the service.

The #persisted? method was added to show a clearer intent and also offer
minimal ActiveModel interface
[docs::was::storage] i was wrong. this is an int describing "number of seconds before expiration"
to confirm, go to -- http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html
search for -- expires
[docs::was::storage] formatting
[docs::was::storage] added more description
[docs::was::storage] added docs for other public methods
[docs::was::storage] added URL for list of S3 docs about Restful HTTP API
[docs::was::storage] this consistently spaces all methods 2 lines from each other
[vsphere] allow to create a vm with multiple disks.

unitNumber has to be unique.
add IamInstanceProfile abilitie
[docs] changed rdoc formatting to yard
skype sucks
fix existing spot specs
support parsing the iamInstanceProfile
remove docs and related, they now live at fog/fog.github.com
update copyright notice year
rescue/retry when loading gems (possibly without rubygems)
closes #901
[docs::aws::storage] added [] to make it pretty
[docs::aws::storage] yard doc syntax fix
[docs::aws::storage] reformatted copy_object
[docs::aws::storage] reformatted delete requests