Feature request: generate attributes by fixed RNG

[purintai]

seed データ生成時などに出力結果が固定できると便利そうなので、乱数生成器を Config 経由で設定できるようにしてみました

irb(main):001:0> require 'gimei'
=> true
irb(main):002:0> Gimei.config.rng = Random.new(1234)
=> #<Random:0x00007fad24009028>
irb(main):003:0> Gimei.name
=> #<Gimei::Name:0x00007fad1f9bae50 @gender=:female, @first=#<Gimei::Name::First:0x00007fad1f9bae00 @gender=:female, @name=#<Gimei::Name::NameWord:0x00007fad1f9bad88 @name=["祐里", "ゆうり", "ユウリ"]>>, @last=#<Gimei::Name::Last:0d1f9bad60 @name=#<Gimei::Name::NameWord:0x00007fad1f9bad10 @name=["戸田", "とだ", "トダ"]>>>
irb(main):004:0> Gimei.name
=> #<Gimei::Name:0x00007fad1f9b88d0 @gender=:female, @first=#<Gimei::Name::First:0x00007fad1f9b8880 @gender=:female, @name=#<Gimei::Name::NameWord:0x00007fad1f9b8808 @name=["美佐", "みさ", "ミサ"]>>, @last=#<Gimei::Name::Last:0x000f9b87e0 @name=#<Gimei::Name::NameWord:0x00007fad1f9b8790 @name=["松浦", "まつうら", "マツウラ"]>>>
irb(main):005:0> Gimei.config.rng = Random.new(1234)
=> #<Random:0x00007fad1fac3d10>
irb(main):006:0> Gimei.name
=> #<Gimei::Name:0x00007fad1fac1ba0 @gender=:female, @first=#<Gimei::Name::First:0x00007fad1fac1b50 @gender=:female, @name=#<Gimei::Name::NameWord:0x00007fad1fac1ad8 @name=["祐里", "ゆうり", "ユウリ"]>>, @last=#<Gimei::Name::Last:0d1fac1ab0 @name=#<Gimei::Name::NameWord:0x00007fad1fac1a60 @name=["戸田", "とだ", "トダ"]>>>
irb(main):007:0> Gimei.name
=> #<Gimei::Name:0x00007fad2030f5f0 @gender=:female, @first=#<Gimei::Name::First:0x00007fad2030f5a0 @gender=:female, @name=#<Gimei::Name::NameWord:0x00007fad2030f528 @name=["美佐", "みさ", "ミサ"]>>, @last=#<Gimei::Name::Last:0x000030f500 @name=#<Gimei::Name::NameWord:0x00007fad2030f4b0 @name=["松浦", "まつうら", "マツウラ"]>>>

[coveralls]

Coverage remained the same at 100.0% when pulling 785e1ac on purintai:fixed_rng into de6efc7 on willnet:master.

[willnet]