Fix Chef 11 compatibility when enumerating EBS volumes to create

Attribute arrays are immutable. The `dup` in `reject` preserved immutability
causing an exception when truncating members.
Allow device override in databag to match EBS naming scheme

Some kernels attach EBS devices to /dev/xvd* instead of /dev/sd*. The data
recipe expects the device name to reflect the OS for formatting, but the EBS API
always uses /dev/sd*. This change allows a databag to explicitly declare what
EBS will use for the device name via `ebs.device`.

Closes #74
Added IAM instance profile support for AWS credentials

The Fog gem already supports IAM instance profiles. This adds support
into the EBS cookbook recipe.

Closes #72