refactor(commands): separate commands and its core into two folders (#32)

- I think it would be better if one for commands only, one for the spec
handling core logic so people won't be confused by the core logic inside
the commands folder (cleaner I guess)
- Regen docs

commands/ops/tailscale.go

@@ -1,14 +1,14 @@
 package ops
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "tailscale",
 		Description: "Connect to Tailscale, logging in if needed",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "up", Description: "Connect to Tailscale, logging in if needed"},
 			{Name: "down", Description: "Disconnect from Tailscale"},
 			{Name: "logout", Description: "Disconnect from Tailscale and expire current node key"},
@@ -27,7 +27,7 @@ func init() {
 			{Name: "cert", Description: "Get TLS certs"},
 			{Name: "help", Description: "Print help message"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--accept-dns", Description: "Accept DNS configuration from the admin panel"},
 			{Name: "--accept-routes", Description: "Accept routes advertised by other Tailscale nodes"},
 			{Name: "--advertise-exit-node", Description: "Offer to be an exit node for internet traffic for the tailnet"},