Kender suppressing system call errors

[uchittamuru-mdsol]

When system call (bundle exec shamus) execution fails, kender is suppressing the reason behind the failure and just saying Run time error with an error code ( https://github.com/mdsol/kender/blob/master/lib/kender/command.rb#l24), instead it would be quite useful if the reason for the failure is printed out. I looked up on the net and found the following a better way to handle system call errors.

begin
  %x[system_call]
rescue Exception => e
  puts e.message
end

[asmith-mdsol]

That's a really good idea @uchittamuru-mdsol! Something we might also look to do in Ruby 1.9+ is use popen3 or similar so that we can manage both STDOUT and STDERR (if that's actually necessary). If you like to open a PR, please go ahead!