All tags should implement hashCode()

[Querz]

As all Tags override equals(), they must also override hashCode() correctly. See #15

[coveralls]

Pull Request Test Coverage Report for Build 141

• 11 of 11 (100.0%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 97.362%

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Totals
Change from base Build 133:	0.02%
Covered Lines:	1218
Relevant Lines:	1251

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💛 - Coveralls