Enable JRuby testing for Action Mailer
Enable JRuby testing for Action Mailer

All tests passing locally for me:

```
195 runs, 441 assertions, 0 failures, 0 errors, 0 skips
```

felipecvo/rails,EmmaB/rails-1,brchristian/rails,iainbeeston/rails,baerjam/rails,prathamesh-sonpatki/rails,illacceptanything/illacceptanything,MSP-Greg/rails,yawboakye/rails,marklocklear/rails,repinel/rails,gfvcastro/rails,eileencodes/rails,BlakeWilliams/rails,rbhitchcock/rails,brchristian/rails,pschambacher/rails,aditya-kapoor/rails,kirs/rails-1,MSP-Greg/rails,mtsmfm/railstest,illacceptanything/illacceptanything,kaspth/rails,illacceptanything/illacceptanything,kaspth/rails,eileencodes/rails,esparta/rails,kirs/rails-1,yawboakye/rails,georgeclaghorn/rails,esparta/rails,assain/rails,Edouard-chin/rails,kddeisz/rails,palkan/rails,yhirano55/rails,repinel/rails,ngpestelos/rails,rafaelfranca/omg-rails,schuetzm/rails,kddeisz/rails,esparta/rails,iainbeeston/rails,kmayer/rails,yasslab/railsguides.jp,Envek/rails,odedniv/rails,joonyou/rails,kirs/rails-1,deraru/rails,lcreid/rails,mathieujobin/reduced-rails-for-travis,deraru/rails,palkan/rails,hanystudy/rails,stefanmb/rails,Erol/rails,bradleypriest/rails,shioyama/rails,utilum/rails,rbhitchcock/rails,yalab/rails,illacceptanything/illacceptanything,tjschuck/rails,Edouard-chin/rails,betesh/rails,xlymian/rails,illacceptanything/illacceptanything,Envek/rails,joonyou/rails,illacceptanything/illacceptanything,mtsmfm/railstest,kmcphillips/rails,gfvcastro/rails,tijwelch/rails,matrinox/rails,yahonda/rails,maicher/rails,shioyama/rails,marklocklear/rails,utilum/rails,Erol/rails,gcourtemanche/rails,illacceptanything/illacceptanything,jeremy/rails,maicher/rails,coreyward/rails,bogdanvlviv/rails,Spin42/rails,arunagw/rails,gavingmiller/rails,ngpestelos/rails,joonyou/rails,assain/rails,deraru/rails,BlakeWilliams/rails,aditya-kapoor/rails,flanger001/rails,Spin42/rails,xlymian/rails,travisofthenorth/rails,pvalena/rails,fabianoleittes/rails,eileencodes/rails,yahonda/rails,printercu/rails,schuetzm/rails,rbhitchcock/rails,untidy-hair/rails,prathamesh-sonpatki/rails,Envek/rails,assain/rails,mijoharas/rails,mtsmfm/railstest,yhirano55/rails,Sen-Zhang/rails,matrinox/rails,rossta/rails,riseshia/railsguides.kr,samphilipd/rails,rails/rails,mechanicles/rails,voray/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,MSP-Greg/rails,tijwelch/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,mtsmfm/rails,coreyward/rails,schuetzm/rails,koic/rails,betesh/rails,mtsmfm/rails,ttanimichi/rails,alecspopa/rails,samphilipd/rails,gauravtiwari/rails,ttanimichi/rails,rossta/rails,richseviora/rails,iainbeeston/rails,EmmaB/rails-1,xlymian/rails,utilum/rails,untidy-hair/rails,yhirano55/rails,baerjam/rails,richseviora/rails,tgxworld/rails,untidy-hair/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,tgxworld/rails,bradleypriest/rails,fabianoleittes/rails,baerjam/rails,mechanicles/rails,ledestin/rails,iainbeeston/rails,starknx/rails,yalab/rails,kamipo/rails,hanystudy/rails,bolek/rails,kmcphillips/rails,starknx/rails,Vasfed/rails,pschambacher/rails,coreyward/rails,elfassy/rails,rails/rails,tjschuck/rails,aditya-kapoor/rails,assain/rails,prathamesh-sonpatki/rails,kachick/rails,tjschuck/rails,printercu/rails,kddeisz/rails,tgxworld/rails,Stellenticket/rails,yahonda/rails,georgeclaghorn/rails,starknx/rails,BlakeWilliams/rails,mtsmfm/rails,schuetzm/rails,bolek/rails,repinel/rails,gcourtemanche/rails,odedniv/rails,Stellenticket/rails,palkan/rails,mathieujobin/reduced-rails-for-travis,odedniv/rails,fabianoleittes/rails,yhirano55/rails,ngpestelos/rails,flanger001/rails,EmmaB/rails-1,sealocal/rails,riseshia/railsguides.kr,sealocal/rails,mijoharas/rails,riseshia/railsguides.kr,travisofthenorth/rails,alecspopa/rails,georgeclaghorn/rails,bradleypriest/rails,printercu/rails,notapatch/rails,kachick/rails,shioyama/rails,lcreid/rails,jeremy/rails,rossta/rails,matrinox/rails,felipecvo/rails,pvalena/rails,kmcphillips/rails,kmcphillips/rails,yasslab/railsguides.jp,Edouard-chin/rails,Erol/rails,mechanicles/rails,prathamesh-sonpatki/rails,voray/rails,gauravtiwari/rails,shioyama/rails,voray/rails,richseviora/rails,tjschuck/rails,utilum/rails,mohitnatoo/rails,arunagw/rails,Envek/rails,bogdanvlviv/rails,sealocal/rails,riseshia/railsguides.kr,lcreid/rails,alecspopa/rails,mechanicles/rails,marklocklear/rails,betesh/rails,deraru/rails,Stellenticket/rails,baerjam/rails,flanger001/rails,yahonda/rails,stefanmb/rails,ledestin/rails,notapatch/rails,yalab/rails,Stellenticket/rails,mijoharas/rails,lucasmazza/rails,rails/rails,gfvcastro/rails,bogdanvlviv/rails,kmayer/rails,untidy-hair/rails,mathieujobin/reduced-rails-for-travis,brchristian/rails,Sen-Zhang/rails,lcreid/rails,notapatch/rails,kenta-s/rails,yawboakye/rails,MSP-Greg/rails,jeremy/rails,rafaelfranca/omg-rails,eileencodes/rails,yalab/rails,printercu/rails,travisofthenorth/rails,vipulnsward/rails,Vasfed/rails,felipecvo/rails,mohitnatoo/rails,BlakeWilliams/rails,tijwelch/rails,kaspth/rails,Erol/rails,vipulnsward/rails,betesh/rails,hanystudy/rails,georgeclaghorn/rails,gavingmiller/rails,pvalena/rails,travisofthenorth/rails,ttanimichi/rails,Edouard-chin/rails,illacceptanything/illacceptanything,repinel/rails,lucasmazza/rails,elfassy/rails,kamipo/rails,Vasfed/rails,arunagw/rails,bolek/rails,gavingmiller/rails,stefanmb/rails,yasslab/railsguides.jp,bogdanvlviv/rails,kmayer/rails,arunagw/rails,gauravtiwari/rails,lucasmazza/rails,palkan/rails,koic/rails,vipulnsward/rails,kenta-s/rails,kenta-s/rails,yasslab/railsguides.jp,jeremy/rails,samphilipd/rails,kamipo/rails,aditya-kapoor/rails,pschambacher/rails,illacceptanything/illacceptanything,notapatch/rails,koic/rails,ledestin/rails,pvalena/rails,mohitnatoo/rails,kachick/rails,Sen-Zhang/rails,joonyou/rails,mohitnatoo/rails,gfvcastro/rails,yawboakye/rails,flanger001/rails,tgxworld/rails,Spin42/rails,gcourtemanche/rails,fabianoleittes/rails,rafaelfranca/omg-rails,vipulnsward/rails,rails/rails,kddeisz/rails,maicher/rails,elfassy/rails,Vasfed/rails,esparta/rails