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/text/vale.go

@@ -1,19 +1,19 @@
 package text
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "vale",
 		Description: "A syntax-aware linter for prose built with speed and extensibility in mind",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "ls-config", Description: "Print the current configuration to stdout"},
 			{Name: "ls-metrics", Description: "Print the given file's internal metrics to stdout"},
 			{Name: "file", Description: "The path to a file you want to analyze"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--help", Description: "Show help for vale"},
 			{Name: "--version", Description: "Print the current version"},
 			{Name: "--ignore-syntax", Description: "Lint all files line-by-line"},