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/elm_json.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:        "elm-json",
 		Description: "Deal with your elm.json",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "help", Description: "Prints help information or the help of the given subcommand(s)"},
 			{Name: "install", Description: "Install a package"},
 			{Name: "PACKAGE", Description: "Package to install, e.g. elm/core or elm/core@1.0.2 or elm/core@1"},
@@ -18,7 +18,7 @@ func init() {
 			{Name: "upgrade", Description: "Bring your dependencies up to date"},
 			{Name: "INPUT", Description: "The elm.json file to upgrade [default: elm.json]"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--help", Description: "Prints help information"},
 			{Name: "--test", Description: "Install as a test-dependency"},
 			{Name: "--version", Description: "Prints version information"},