`sort` and `sort_type` have been renamed in the API, breaking pagination

[aaronsnoswell]

Hello!

I have been trying to get psaw working today and discovered that the sort and sort_type query fields have been renamed.

According to a comment on the r/Pushshift subreddit;

• sort is now called order, and
• sort_type is now called sort

This breaks the psaw library as sort=desc (which is appended to queries with no sort field) now triggers an HTTP 442 error, and specifying sort=None breaks pagination.

I've modded my local install of psaw to work, and will attempt to prepare a PR for the library.