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/git/git_flow.go

@@ -1,14 +1,14 @@
 package git
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "git-flow",
 		Description: "Git extensions to provide high-level repository operations for Vincent Driessen's branching model",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "init", Description: "Initialize a new git repo with support for the branching model"},
 			{Name: "feature", Description: "List all feature branches"},
 			{Name: "start", Description: "Create a new feature branch"},
@@ -21,7 +21,7 @@ func init() {
 			{Name: "hotfix", Description: "List all hotfix branches"},
 			{Name: "support", Description: "List all support branches"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-d", Description: "Use default branch naming conventions"},
 			{Name: "-f", Description: "Force setting of gitflow branches, even if already configured"},
 		},