Real network test cases executor

[Stranger6667]

We need to have some runner abstraction that will be able to execute the given test cases against certain target: URL or WSGI app instance.

For real network case, it would be nice to execute the cases asynchronously for the speed reason. For now, we need only real network executor, WSGI one could be done separately.

Input: Base URL

Output: List of responses. Probably it shouldn't be aiohttp-specific response, might be a simplified structure so alternative executors could make them in the future.

Also, it could be mapping - Case: Response, might be better for the future processing

The core logic here is to convert Case into kwargs for aiohttp so it could make a proper network request

[Stranger6667]

Done in #63