Lots o' changes

- New logging format with winston
- Dynamic route/request bindings
- Configurable default size for avatars
- Better regex matching for requests, usernames, and avatar sizes
- Better error handling and responses
- Better response flow in general
- Reorganized functions in Minecraft Skin API
- Added hard-coded ‘char’ skin for faster response
- Better handling for non-existent skins/users

… and probably much more.