fixed unicode error for ruby versions >= 1.9.0

When trying to install the gem I get the following error message: 

```ruby 
Installing ri documentation for drivenow-1.0.1...
unable to convert "\xC3" from ASCII-8BIT to UTF-8 for lib/drivenow/drivenow_agent.rb, skipping
Installing RDoc documentation for drivenow-1.0.1...
unable to convert "\xC3" from ASCII-8BIT to UTF-8 for lib/drivenow/drivenow_agent.rb, skipping

```