API Example: CSV

This pull request adds a small class to wrap API requests and a CSV exporter as both an example and functional utility. To test this you'll need an API access token. Set API_TOKEN in `docs/api/examples/csv.py` and then invoke csv.py from the command line to try it out.

Example invocation:  `python docs/api/examples/csv.py core/system --limit 250 --params "a:Hardware+type=apple" --fields "id,name" --attributes "Location,Operating System" --delimiter "~" > ../systems.csv`