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/jvm/clojure.go

@@ -1,14 +1,14 @@
 package jvm
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "clojure",
 		Description: "An alias to refer to its function or a qualified function",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-A", Description: "Use concatenated aliases to modify classpath"},
 			{Name: "-X", Description: "Invoke tool by name or via aliases ala -X"},
 			{Name: "-M", Description: "Use concatenated aliases to modify classpath or supply main opts"},