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/k3d.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:        "k3d",
 		Description: "Little helper to run k3s in Docker",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "cluster", Description: "Manage k3s clusters"},
 			{Name: "create", Description: "Create a new k3s cluster"},
 			{Name: "cluster name", Description: "Name of the cluster to create"},
@@ -53,7 +53,7 @@ func init() {
 			{Name: "Registry Name", Description: "Name of the registry"},
 			{Name: "version", Description: "Show k3d and default k3s version"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-a", Description: "Number of agents to create"},
 			{Name: "--agents-memory", Description: "Memory limit imposed on the agents nodes"},
 			{Name: "--api-port", Description: "Specify the Kubernetes API server port exposed on the LoadBalancer"},