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/dscl.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:        "dscl",
 		Description: "Prompt for password",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "read", Description: "Prints a directory"},
 			{Name: "readall", Description: "Prints all the records of a given type"},
 			{Name: "readpl", Description: "Prints the contents of plist_path"},
@@ -24,7 +24,7 @@ func init() {
 			{Name: "passwd", Description: "Changes the password of a user"},
 			{Name: "new password", Description: "New password of the user"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-p", Description: "Prompt for password"},
 			{Name: "-u", Description: "Authenticate as user"},
 			{Name: "-P", Description: "Authenticate with password"},