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/newman.go

@@ -1,18 +1,18 @@
 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:        "newman",
 		Description: "Newman is a command-line collection runner for Postman",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "run", Description: "Initiate a Postman Collection run from a given URL or path"},
 			{Name: "help", Description: "Display help for command"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-e", Description: "Specify a URL or path to a Postman Environment"},
 			{Name: "-g", Description: "Specify a URL or path to a file containing Postman Globals"},
 			{Name: "-r", Description: "Specify the reporters to use for this run"},