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/opa.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:        "opa",
 		Description: "Open Policy Agent (OPA)",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "bench", Description: "Benchmark a Rego query"},
 			{Name: "build", Description: "Build an OPA bundle"},
 			{Name: "check", Description: "Check Rego source files"},
@@ -29,7 +29,7 @@ func init() {
 			{Name: "version", Description: "Print the version of OPA"},
 			{Name: "help", Description: "Help about any command"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--benchmem", Description: "Report memory allocations with benchmark results"},
 			{Name: "--bundle", Description: "Set bundle file(s) or directory path(s). This flag can be repeated"},
 			{Name: "--count", Description: "Number of times to repeat each benchmark"},