gsub! can't modify frozen String using the plot example in Readme #14
Description
/Users/csaba/.rvm/gems/ruby-1.9.3-p194/gems/rsruby-0.5.1.1/lib/rsruby.rb:184:in gsub!': can't modify frozen String (RuntimeError) from /Users/csaba/.rvm/gems/ruby-1.9.3-p194/gems/rsruby-0.5.1.1/lib/rsruby.rb:184:inconvert_method_name'
from /Users/csaba/.rvm/gems/ruby-1.9.3-p194/gems/rsruby-0.5.1.1/lib/rsruby.rb:148:in lcall' from /Users/csaba/.rvm/gems/ruby-1.9.3-p194/gems/rsruby-0.5.1.1/lib/rsruby.rb:148:inmethod_missing'