write_entry: Write an entry to a csv file
In jarad/FluSight: Utility functions for the CDC FluSight competition

Verify an entry and then write it to a csv file

1	write_entry(entry, path, team_name, week = NULL, challenge = "ilinet")

`entry`	An entry data.frame
`path`	A character string specifying a directory for the file
`team_name`	A character string specifying the team name
`week`	A scalar numeric indicating the week number or NULL (default). If NULL, the week will automatically be determined from the current date.
`challenge`	one of "ilinet", "hospital", or "state_ili", indicating which forecasting challenge the entry is for. Default is "ilinet"
`check_week`	A logical value (default 'TRUE') indicating whether to check for the column forecast_week. Should be 'TRUE' if evaluating entry prior to scoring, can be 'FALSE' if evaluating entry prior to writing to disk.