Shall we make it compatible with Ruby 1.8.7? 

Hi Tim, 

Hope all goes well with you! 
This is Mark, a QA from ThoughtWorks China. We have 6 teams here working on web projects that built with Ruby on Rails , and we are all very interested in this amazing DSL for JMeter!  We plan to use this in our daily work and also our Continuous Integration (CI) environment. 
But the problems now is, for some reason, we need to stick  on ruby 1.8.7, instead of ruby 1.9.3, which means, when we use this gem, there will be some error. 
I made some simple changes to make it compatible with ruby 1.8.7. 
This may also make this gem more popular in wider area. 

Could you please help to review my last commit and pull it? Thank you in advance! 

Cheers, 
Mark