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/jq.go

@@ -1,14 +1,14 @@
 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:        "jq",
 		Description: "Output the jq version and exit with zero",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--version", Description: "Output the jq version and exit with zero"},
 			{Name: "--seq", Description: "Parse the input in streaming fashion, outputting arrays of path and leaf values"},
 			{Name: "--slurp", Description: "Use a tab for each indentation level instead of two spaces"},