Specify term association class name in user model.

[stahor]

Some libraries like rails admin work incorrectly without this

[coveralls]

Pull Request Test Coverage Report for Build 95

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.234%

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Totals
Change from base Build 93:	0.0%
Covered Lines:	813
Relevant Lines:	872

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💛 - Coveralls

[michelson]

true. thanks for the addition @stahor !