Must have: apt-get install unoconv

Instructions for working with google documents:

1. visit https://developers.google.com/docs/api/quickstart/ruby?authuser=1
2. click Enable the Google Docs API and choose "Desktop App"
3. In resulting dialog click DOWNLOAD CLIENT CONFIGURATION and save the file
   credentials.json to plugins/redmine_keywords/config/docs-api-credentials.json
4. Run google-auth.rb
5. follow the instructions to get credentials