Use flexidate

[ivanovyordan]

Description of change

Fix #94
Flexidate is a date parser that works well with dates not supported by Python's built-in datetime package.

QA steps

• automated tests passing
• manual qa steps passing (list below)

1. Insert 3 records with 3 different date values - todays date, a BC date and a date in year 10000.
2. Start the initial sync
3. Insert 3 new records with similiar dates
4. Start incremental sync
5. Check the values in the target

Risks

The target needs to handle these dates properly otherwise, there will be a similar error.

Rollback steps

• revert this branch