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/sequelize.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:        "sequelize",
 		Description: "The environment to run the command in",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--env", Description: "The environment to run the command in"},
 			{Name: "--config", Description: "The path to the config file"},
 			{Name: "--options-path", Description: "The path to a JSON file with additional options"},