Progress towards v5

[Syfaro]

This library has unfortunately been a bit neglected lately. I'd like to start getting things moving in the correct direction again, but that depends on merging PRs that break backwards compatibility. Before that happens, I'd like to have more people properly review the code to ensure that there doesn't need to be another set of breaking changes because of overlooked issues.

The current PRs pending merge before v5 can be tagged and merged into master are as follows:

• Deduplicate code, improve response accuracy.  #202
  • The big set of changes for the v5, primarily consisting of internal API improvements
  • Removes superfluous methods that should use the Request method instead
  • Fixes a number of issues with errors that are discarded
  • At this point, I think these changes are probably safe and okay to merge, but please feel free to add a review
• Updates for Bot API 5.0 and 5.1 #392
  • Relatively straightforward changes for Bot API updates
  • Mostly looking to make sure nothing was forgotten or mistyped
• Add support for uploading multiple files #356
  • A big and breaking change to how files are handled, to allow uploading multiple files in a single request
  • This needs the most attention, I'd like to not have to worry about file uploads in the future
  • Is there anything that can be better generalized or further improved?

And are there any other breaking changes that should be made for v5? Given how many changes are being made, I'd like to do them all at once instead of making more problems in the future.

I'm sorry for how long this has taken to happen. I know how frustrating it is to be missing features, especially ones with open pull requests.

If anyone has other questions or thoughts on the subject, please feel free to discuss.