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/sys/codesign.go

@@ -1,14 +1,14 @@
 package sys
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "codesign",
 		Description: "Create and manipulate code signatures",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--all-architectures", Description: "Display information about the code at the path(s) given"},
 			{Name: "-D", Description: "Constructs and prints the hosting chain of a running program"},
 			{Name: "-i", Description: "Indicates the granularity of code signing. Pagesize must be a power of two"},