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/ops/knex.go

@@ -1,14 +1,14 @@
 package ops
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "knex",
 		Description: "SQL query builder for JavaScript",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "init", Description: "Create a fresh knexfile"},
 			{Name: "migrate:make", Description: "Create a named migration file"},
 			{Name: "migrate:latest", Description: "Run all migrations that have not yet been run"},
@@ -22,7 +22,7 @@ func init() {
 			{Name: "seed:run", Description: "Run seed files"},
 			{Name: "help", Description: "Display help for command"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--version", Description: "Output the version number"},
 			{Name: "--debug", Description: "Run with debugging"},
 			{Name: "--knexfile", Description: "Specify the knexfile path"},