add proper support for parsing numbers from a csv

Currently when node-csv parses numbers from a csv file they are interpreted as strings. This adds a regexp to check if the input is a number/float and parses it accordingly. Unit tests have been updated (you lose precision in basic cases i.e. 1974.0 => 1974, but I think this is probably not a concern for those trying to work with the data properly)

I did not include the generated parser.js in this PR, but can add that easily if that's desired.