refactoring suggestions

[gurgeous]

As I'm getting deeper into the project, I had a few ideas for some mild refactors we could consider. Might make it easier for newcomers to jump in. Totally optional, of course, just wanted to bring it up as a topic of discussion. These aren't in order or anything:

1. move http helpers from besticon.go into fetch.go. move color helpers from lettericon.go into color.go. etc.
2. update iconserver HTML, for example removing old references to heroku app
3. add struct for lettericon path parsing
4. I see colorfinder has a main(). does that still work?
5. should we remove FindBestIcon? That confused me at first
6. add type Config & config.go to handle environment variables, command line flags and query arguments
7. fix linting errors (I think vscode is using golint)
8. would it be helpful to centralize utility functions and assertions? I am new to golang, so pardon my ignorance here.
9. finish/document secondary executables (like besticon, icoparser)

Just some random ideas. The project has a great test suite so this kind of work is pretty straightforward.