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/js/vue.go

@@ -1,14 +1,14 @@
 package js
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "vue",
 		Description: "Vue cli tools",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "create", Description: "Create a new project powered by vue-cli-service"},
 			{Name: "add", Description: "Install a plugin and invoke its generator in an already created project"},
 			{Name: "invoke", Description: "Invoke the generator of a plugin in an already created project"},
@@ -23,7 +23,7 @@ func init() {
 			{Name: "migrate", Description: "(experimental) run migrator for an already-installed cli plugin"},
 			{Name: "info", Description: "Print debugging information about your environment"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-p", Description: "Skip prompts and use saved or remote preset"},
 			{Name: "-d", Description: "Skip prompts and use default preset"},
 			{Name: "-i", Description: "Skip prompts and use inline JSON string as preset"},