Major refactor of code base

[NickSeagull]

I refactored the code base, so contributions are (hopefully) easier now.

Changes

• Bumped Stack resolver to lts-13.25
• Removed HLint config file (it was the one from the Relude repo, but we don't use Relude anymore)
• Started using http-client for working with HTTP requests.
• Now we create a single HTTP manager instead of spawning it with each request
• Migrate from an MTL stack to checked exceptions, and work in IO
• Use ByteString and String for mostly everything.
  Removed some Text, because we were converting back and forth from Text and String and we were losing some time with the conversions.