Improve error message in case of a misformatted file (#158)

[joe-at-openai]

• add more descriptive error handling regarding poorly formatted files

• update version

• add dot prefix to json file extentions and ensure list of allowable file types is complete

• cleanup error messages and add comments to explain jsonl/json loading logic

• cleanup csv/tsv reading allowing use of elif for other file extensions, add comments, and remove unnecessary re-attempt to parse as json

• run fillna immediately upon DataFrame creation so that an additional switch is not needed

• use only 1 try-except block to catch parsing errors + cleanup error message

• separate the json and jsonl cases while still maintaining the same functionality, also include a message to user if jsonl appears to be json or vice versa

• fix bug in csv path

• use index -1 to get extension from split

• black formatting apply

• fix black

Co-authored-by: joe-at-openai [email protected]