Improve ergonomics of methods that must return a struct with a lifetime parameter

[Cldfire]

https://github.com/Cldfire/nvml-wrapper/blob/master/src/device.rs#L2945
https://github.com/Cldfire/nvml-wrapper/blob/master/src/device.rs#L3237

This may or may not be possible to do after rust-lang-deprecated/error-chain#48 is resolved.

[Cldfire]

The links above are outdated, but the method in question here is Device.remove. error-chain is no longer used in nvml-wrapper, so this is now fixable.