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/jvm.go

@@ -1,15 +1,15 @@
 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:        "javac",
 		Description: "Java compiler",
-		Generator:   core.FileGenerator(".java"),
-		Options: []core.Option{
+		Generator:   spec.FileGenerator(".java"),
+		Options: []spec.Option{
 			{Name: "-d", Description: "output directory"},
 			{Name: "-cp", Description: "class path"},
 			{Name: "-classpath", Description: "class path (long form)"},
@@ -24,11 +24,11 @@ func init() {
 		},
 	})
 
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "java",
 		Description: "Java runtime",
-		Generator:   core.FileGenerator(".jar", ".class"),
-		Options: []core.Option{
+		Generator:   spec.FileGenerator(".jar", ".class"),
+		Options: []spec.Option{
 			{Name: "-jar", Description: "run jar file"},
 			{Name: "-cp", Description: "class path"},
 			{Name: "-Xmx", Description: "max heap size (e.g. -Xmx512m)"},
@@ -41,11 +41,11 @@ func init() {
 		},
 	})
 
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "kotlinc",
 		Description: "Kotlin compiler",
-		Generator:   core.FileGenerator(".kt", ".kts"),
-		Options: []core.Option{
+		Generator:   spec.FileGenerator(".kt", ".kts"),
+		Options: []spec.Option{
 			{Name: "-d", Description: "output dir or jar"},
 			{Name: "-cp", Description: "class path"},
 			{Name: "-include-runtime", Description: "include runtime in jar"},