Cosmetic: eliminate dead code, learn how it works

I took out the “version” option. I think we should have a more general
way to ask things like “info”. Maybe something like this:

     elm-get info evancz/automaton
     elm-get info evancz/automaton --version
     elm-get info evancz/automaton --dependencies
Redirect to latest version with /latest path
Make sure docs.json is loaded up regardless of trailing slash
Add note about how to link to "latest" version
Loosen up dependencies
change format of HTTP errors to be more helpful
Add dependency on TLS library

Also remove stray prints used for debugging
Rework Install interaction to get rid of redundant interactions
Use style consistent with rest of the repo