Fixed issue with relationship between OrderResponses and AssetResponses

Breaking release for the OrderResponse and AssetResponse classes.
Essentially I found out OpenSea returns sell order data when using the AssetsEndpoint.
I adapted the related Response classes to include the sell order data aswell, but this brought about a breaking fix.
I had to move OrderResponse from it's own py file into the py file containing AssetResponse.

Other:
Added more documentation in the README file.

Implemented async get requests

In addition to adding API key handling, I also completely replaced the get request functionality with a asynchronous implementation.
This is a breaking change from previous releases, but allows for much faster data retrieval!

The API key is automatically detected if you registered it as the OPENSEA_API_KEY variable in your system variables.
Otherwise, you need to pass it into each instance of ClientParams before instantiating an endpoint.

Fixes to Pagination function and Event response objects

Fixes:

• Resolved pagination issue where pagination used to end too early.
• Events response object uses .get() method now to accomodate different EventType HTTP responses.

Minor things:

• removed outdated docstring, lowered ratelimiter frequency
• Various typehint error fixes.
• Fixed some duplicate tests coming from git merge/rebase mistakes.

Added minor validation method to the OrdersEndpoint

Added logger message when pagination method encounters an HTTP Error.
Added validation method on the OrdersEndpoint to verify that the token_ids attribute is no longer than 30 in length.

Removed mention of a retry parameter for the BaseClient class, this is not yet implemented

Added minor validation method to the OrdersEndpoint

Added logger message when pagination method encounters an HTTP Error.
Added validation method on the OrdersEndpoint to verify that the token_ids attribute is no longer than 30 in length.

Implemented OrdersEndpoint and OrderResponse

Major updates

• Implemented OrdersEndpoint and OrderResponse.
• Implemented get_request rate limiter to all endpoints.

Minor updates

• EventResponse: added missing is_private as an optional response attribute.
• Refactor: passed parsing of http response responsibility to the BaseClient ABC class.
• Hotfix: prevent json() from raising exception when http_response is empty
• Hotfix: removed token_id as a possible order_by parameter for Asset endpoint.

Implemented CollectionsEndpoint

Implemented CollectionsEndpoint.
Added extra doc strings to events and assets endpoints.

Important fixes

Documentation:

• README.md: Added some basic information about the package.

Testing:

• Added test runner, all tests pass.

Fixes:

• Minor fix: poorly coded paginator was tested and fixed.
• Minor fix: changed id attributes from responses from int to str.

Various issues fixed, added convenience methods.

Added various validation checks.
Fixed issue with remaining pages func.
Adjusted load methods on response parser class.
Added str methods on multiple Response classes.
Fixed Traits/Last Sale in AssetResponse class .

Project structure change & Tested Paginator

v0.4.0-dev

Project structure changes, and added tests to endpoint paginator method.