Add some deprecation warnings

[sajith]

Resolves #293. Changes:

• Uses @deprecated decorator from deprecated library. This is a small library with a single dependency, and the ability to add deprecation notices to Sphinx-generated docs is a fairly good justification for adding a dependency.
• Adds a couple of unit tests.

[coveralls]

Pull Request Test Coverage Report for Build 8668449895

Details

• 23 of 23 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.1%) to 24.056%

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Totals
Change from base Build 8559162669:	2.1%
Covered Lines:	1273
Relevant Lines:	4722

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💛 - Coveralls

[kthare10]

Looks good!

[nbastin]

These tests can't possibly fail. This is not ok.

[kthare10]

@sajith - The deprecated function get_physical_os_device_name() is being used by several list/show functions within fablib. Please verify changing it to the newer function that's suggested and update the code accordingly.