Give documentation some ❤️

[10xSebastian]

• Merges all the sub documentations, to the main readme
• Restructures the whole documentation (README) into the following chapters: Request, Response, Exceptions, Configuration, Interceptors
• Deletes all those standalone documentation files (after merging/updating them)
• Updates the gem description
• Bumps the patch level (version) to release the new gem description to rubygems

Here is how the new documentation will look like: https://github.com/local-ch/lhc/blob/c40685f497b640bb4df907fb560407002336b475/README.md