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/tmuxinator.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:        "tmuxinator",
 		Description: "Project",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "commands", Description: "Lists commands available in tmuxinator"},
 			{Name: "completions", Description: "Used for shell completion"},
 			{Name: "copy", Description: "Copy an existing project to a new project and open it in your editor"},
@@ -33,7 +33,7 @@ func init() {
 			{Name: "stop", Description: "Stop a tmux session using a project's tmuxinator config"},
 			{Name: "version", Description: "Display installed tmuxinator version"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-a", Description: "Attach to tmux session after creation"},
 			{Name: "-n", Description: "Give the session a different name"},
 			{Name: "-p", Description: "Path to project config file"},