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/asciinema.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:        "asciinema",
 		Description: "Terminal session recorder",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "rec", Description: "Start a recording"},
 			{Name: "play", Description: "Replay recorded asciicast in a terminal"},
 			{Name: "seconds", Description: "Can be fractional"},
@@ -17,7 +17,7 @@ func init() {
 			{Name: "upload", Description: "Upload recorded asciicast to asciinema.org site"},
 			{Name: "auth", Description: "Link and manage your install ID with your asciinema.org user account"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--version", Description: "Output version information and exit"},
 			{Name: "-h", Description: "Output help message and exit"},
 			{Name: "--stdin", Description: "Enable stdin (keyboard) recording"},