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_format.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-format",
 		Description: "Format your code in the Elm idiomatic way",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--help", Description: "Show help for elm-format"},
 			{Name: "--output", Description: "Write output to FILE instead of overwriting the given source file"},
 			{Name: "--yes", Description: "Reply 'yes' to all automated prompts"},