Select method changes and docs

[igorbenav]

Pull Request Template for FastCRUD

Description

This is essentially a bug fix + docs for #28 by @dubusster

Changes

• bug fix
• docstring enhanced
• docs added both in usage and advanced

Tests

• more tests
• tests reformatted to multiple functions

Detailed Bug Fix

In select, checking whether sort_columns are provided were written as follows:

if "sort_columns":
           stmt = self._apply_sorting(stmt, sort_columns, sort_orders)

Which was fixed to:

if sort_columns:
           stmt = self._apply_sorting(stmt, sort_columns, sort_orders)

[igorbenav]

Hey, @dubusster, do you want to take a look?

[dubusster]

Oups, thanks for the fix and the additional tests @igorbenav!

[dubusster]

I'll have a look tomorrow to maybe add some more detailed tests

[dubusster]

I also missed some typing in fast_crud.py