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/webpack.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:        "webpack",
 		Description: "Run webpack (default command, can be omitted)",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "build", Description: "Run webpack (default command, can be omitted)"},
 			{Name: "configtest", Description: "Validate a webpack configuration"},
 			{Name: "config-path", Description: "Path to the webpack configuration file"},
@@ -20,7 +20,7 @@ func init() {
 			{Name: "serve", Description: "Run the webpack development server"},
 			{Name: "watch", Description: "Run webpack and watch for file changes"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--config", Description: "Provide path to a webpack configuration file e.g. ./webpack.config.js"},
 			{Name: "--config-name", Description: "Name of the configuration to use"},
 			{Name: "--merge", Description: "Merge two or more configurations using 'webpack-merge'"},