References
- http://julia.readthedocs.org/en/latest/manual/
- http://dataframesjl.readthedocs.io/en/latest/
- https://data.gov.uk/dataset/road-accidents-safety-data
- Wickham, Hadley. "The split-apply-combine strategy for data analysis." Journal of Statistical Software 40.1 (2011): 1-29