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/cc/zig.go

@@ -1,14 +1,14 @@
 package cc
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "zig",
 		Description: "Enable or disable colored message",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "build", Description: "Build project from build.zig"},
 			{Name: "install", Description: "Copy build artifacts to prefix path"},
 			{Name: "uninstall", Description: "Remove build artifacts from prefix path"},
@@ -40,7 +40,7 @@ func init() {
 			{Name: "version", Description: "Print version number and exit"},
 			{Name: "zen", Description: "Print Zen of Zig and exit"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--color", Description: "Enable or disable colored message"},
 			{Name: "--cache-dir", Description: "Override path to local Zig cache directory"},
 			{Name: "--global-cache-dir", Description: "Override path to global Zig cache directory"},