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/runner/gem.go

@@ -1,14 +1,14 @@
 package runner
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "gem",
 		Description: "Use HTTP proxy for remote operations",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "help", Description: "Help about any command"},
 			{Name: "install", Description: "Install a gem into the local repository"},
 			{Name: "PLATFORM", Description: "The platform of gem"},
@@ -60,7 +60,7 @@ func init() {
 			{Name: "GEM", Description: "Name of gem"},
 			{Name: "uninstall", Description: "Uninstall gems from the local repository"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-p", Description: "Use HTTP proxy for remote operations"},
 			{Name: "--no-http-proxy", Description: "Do not use HTTP proxy for remote operations"},
 			{Name: "-l", Description: "Restrict operations to the LOCAL domain"},