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/helmfile.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:        "helmfile",
 		Description: "Deploy helm charts",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "apply", Description: "Apply all resources from state file only when there are changes"},
 			{Name: "build", Description: "Build all resources from state file"},
 			{Name: "cache", Description: "Cache management"},
@@ -25,7 +25,7 @@ func init() {
 			{Name: "test", Description: "Test charts from state file (helm test)"},
 			{Name: "version", Description: "Print the CLI version"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--help", Description: "Do not exit with an error code if the provided selector has no matching releases"},
 			{Name: "--allow-no-matching-release", Description: "Show help for helmfile"},
 			{Name: "--chart", Description: "Output with color"},