Fix incorrect RackTest driver example, closes #1147
Fix incorrect RackTest driver example, closes #1147

The `:browser` option is supported by Selenium, but not by RackTest, seems like this was a copy-paste error.
teamcapybara/capybara,gonzedge/capybara,teamcapybara/capybara,y-yagi/capybara,ksmaheshkumar/capybara,jillianrosile/capybara,soutaro/capybara,twalpole/capybara,Bartuz/capybara,irfanah/capybara,DariaKalynovska/capybara,DariaKalynovska/capybara,khaidpham/capybara,sideci-sample/sideci-sample-capybara,jnicklas/capybara,DariaKalynovska/capybara,mohanraj1311/capybara,tjouan/capybara,teamcapybara/capybara,mohanraj1311/capybara,tjgrathwell/capybara,Bartuz/capybara,jillianrosile/capybara,ducthanh/capybara,twalpole/capybara,twalpole/capybara,pombredanne/capybara,olivierlacan/capybara,wenbofantasy/capybara,gonzedge/capybara,jnicklas/capybara,soutaro/capybara,pombredanne/capybara,wenbofantasy/capybara,ksmaheshkumar/capybara,shepmaster/capybara,tjgrathwell/capybara,olivierlacan/capybara,jillianrosile/capybara,randoum/capybara,y-yagi/capybara,ngpestelos/capybara,mlarraz/capybara,jnicklas/capybara,mreinsch/capybara,mlarraz/capybara,ngpestelos/capybara,soutaro/capybara,ducthanh/capybara,shepmaster/capybara,khaidpham/capybara,tjouan/capybara,ducthanh/capybara,mohanraj1311/capybara,olivierlacan/capybara,tjouan/capybara,randoum/capybara,shepmaster/capybara,mlarraz/capybara,ngpestelos/capybara,sideci-sample/sideci-sample-capybara,ksmaheshkumar/capybara,y-yagi/capybara,pombredanne/capybara,irfanah/capybara,mreinsch/capybara,randoum/capybara,Bartuz/capybara,tjgrathwell/capybara,khaidpham/capybara,gonzedge/capybara,irfanah/capybara