Minor fix to Google pie chart helper

Added 
```ruby 
require 'cgi'
``` 
to the file ```ui/helpers/google_pie_chart.rb``` in order to fix a ```NameError``` that occurred in developer mode when viewing details summary.

Travis tests pass for all environments except ree; that environment seems to be missing bundler, which has nothing to do with my change.  See test results at 
https://travis-ci.org/nihonjinrxs/rpm