Update gemspec

[yukihirop]

Summary

• Specify dependency gem version

[coveralls]

Pull Request Test Coverage Report for Build 90

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 74 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-12.04%) to 87.64%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
spec/fcoin_spec.rb	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
spec/fcoin/endpoint/accounts_spec.rb	2	100.0%
spec/fcoin/endpoint/orders_spec.rb	2	98.79%
spec/fcoin/request_spec.rb	2	100.0%
spec/fcoin/api_spec.rb	4	100.0%
spec/fcoin/configuration_spec.rb	4	100.0%
spec/fcoin/endpoint/public_spec.rb	8	100.0%
spec/fcoin/endpoint/market_spec.rb	52	100.0%

Totals
Change from base Build 87:	-12.04%
Covered Lines:	546
Relevant Lines:	623

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💛 - Coveralls