Replace aiohttp with a non async http library

After learning a lot on differences between mono-thread async, concurrency, parallel execution, threads, etc, I came to the conclusion that aiohttp is:

• Overkill for the DuniterPy usage.
• Hard to implement (need an async loop, recursively add async and await keywords on all functions).
• Not used in terminal little scripts, only in Sakia (may be Silkaj?).

So I want to get rid of aiohttp library and replace it with, to choose:

• urllib (low-level but standard python module)
• requests (high-level but external dependency)

Pro:

• The developers will be able to choose their own concurrency method if needed.
• The library usage will be more simple for everyone (no more async loop and keywords to understand).
• Maintainers will have a simpler code to maintain.

Con:

• Mostly all of the code must be refactored.
• May not be ready for 1.0, but for 2.0.