source-file: NaN is not a valid JSON value

[ChristopheDuong]

Expected Behavior

If the file that is being replicated contains float/double columns with NaN values, source-file should transmit valid RECORD Airbyte Messages.

Current Behavior

Tell us what happens instead of the expected behavior.
The source-file python code is reading/parsing the file fine but when emitting the values into the JSON stream for transit via airbyte protocol, it is not well recognized/parsed and output 'ERROR' messages in the integrationRunner class (line 133) as it wasn't able to properly read the JSON stream. (NaN is not a valid value for numbers in JSON)

Steps to Reproduce

1. For example you can setup the source-file to replicate the following csv file:
   https://raw.githubusercontent.com/opencovid19-fr/data/master/dist/chiffres-cles.csv
2. No data rows is being replicated as all the rows contains NaN values...

Severity of the bug for you

Medium