Fix gem name

$ gem install webdriver
ERROR:  Could not find a valid gem 'webdriver' (>= 0) in any repository
Add run command

ruby sauce_example.rb does nothing because the example uses rspec.
Merge pull request #140 from bootstraponline/patch-1

Fix gem name
Merge pull request #141 from jlipps/master

fixes to ruby examples and execute.js
Exit after scenario

Instruments never exits if quit isn't called.
Merge pull request #142 from bootstraponline/exit_cucumber

Exit after scenario
update readme to reflect info about using wd dev