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/mkdocs.go

@@ -1,20 +1,20 @@
 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:        "mkdocs",
 		Description: "Project documentation with Markdown",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "build", Description: "Build the MkDocs documentation"},
 			{Name: "gh-deploy", Description: "Deploy your documentation to GitHub Pages"},
 			{Name: "new", Description: "Create a new MkDocs project"},
 			{Name: "serve", Description: "Run the builtin development server"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-h", Description: "Provide a specific MkDocs config"},
 			{Name: "-s", Description: "Enable strict mode. This will cause MkDocs to abort the build on any warnings"},
 			{Name: "-t", Description: "The theme to use when building your documentation"},