Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

env/server.go

@@ -1,33 +0,0 @@
-package env
-
-import (
-	"io"
-	"net/http"
-)
-
-// TODO: Move this into dis!
-
-// Server represents a server for this distillery
-type Server struct {
-	dis *Distillery
-}
-
-func (dis *Distillery) Server() *Server {
-	return &Server{
-		dis: dis,
-	}
-}
-
-func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	instances, err := s.dis.AllInstances()
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		io.WriteString(w, "Something went wrong")
-		return
-	}
-
-	w.WriteHeader(http.StatusOK)
-	for _, instance := range instances {
-		io.WriteString(w, instance.Slug+"\n")
-	}
-}