Data science up for first round of review

1) Focus on rspec tests 
2) Stuck at trying to refactor the exception part
filename variable is never used. Either remove it as a method argument altogether or set a default:
`def self.parse(filename='some_file.json')` then use the variable name under `file_read = open(filename).read` you could also omit this line completely and pass the function directly into JSON.parse `json_rows = JSON.parse(open(filename).read)`