Added file_name + '_steps.rb' as a possible alternative for feature files.

I updated the Cucumber file settings to look for the corresponding '_step.rb' file names when using the command to switch between code and tests to make it easier to navigate between feature files and step definitions.

By convention, I store my feature step implementations in file_name_steps.rb files. I believe this is a pretty common convention for Cucumber. 

I love the RubyTest SwitchBetweenCodeAndTest functionality and I'm always hitting the command when reading a feature... This addresses that issue!