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/sanity.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:        "sanity",
 		Description: "Displays help information about Sanity",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "help", Description: "Displays help information about Sanity"},
 			{Name: "build", Description: "Builds the current Sanity configuration to a static bundle"},
 			{Name: "codemod", Description: "Runs a code modification script"},
@@ -48,7 +48,7 @@ func init() {
 			{Name: "invite", Description: "Invite a new user to the project"},
 			{Name: "versions", Description: "Shows the installed versions of Sanity CLI and core components"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--source-maps", Description: "Enable source maps for built bundles (increases size of bundle)"},
 			{Name: "--no-minify", Description: "Skip minifying built JavaScript (speeds up build, increases size of bundle)"},
 			{Name: "-y", Description: "Use unattended mode, accepting defaults and using only flags for choices"},