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/ops/tsuru.go

@@ -1,14 +1,14 @@
 package ops
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "tsuru",
 		Description: "Plan",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "app", Description: "App commands"},
 			{Name: "build", Description: "Builds a tsuru app image respecting"},
 			{Name: "create", Description: "Creates a new app using the given name and platform"},
@@ -53,7 +53,7 @@ func init() {
 			{Name: "login", Description: "Login to tsuru server"},
 			{Name: "logout", Description: "Logout from tsuru server"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-a", Description: "App name"},
 			{Name: "-o", Description: "Filter applications by pool"},
 			{Name: "-p", Description: "Filter applications by platform"},