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/sys/publish.go

@@ -1,19 +1,19 @@
 package sys
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "publish",
 		Description: "Set up a new website in the current folder",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "new", Description: "Set up a new website in the current folder"},
 			{Name: "deploy", Description: "Generate and deploy the website in the current folder"},
 			{Name: "generate", Description: "Generate the website in the current folder"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-p", Description: "Customize the port"},
 			{Name: "--help", Description: "Show help for publish"},
 		},