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/sys/env.go

@@ -4,11 +4,11 @@ import (
 	"os"
 	"strings"
 
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
-func envVarGenerator(tokens []string, _ string, _ string) []core.Suggestion {
-	var results []core.Suggestion
+func envVarGenerator(tokens []string, _ string, _ string) []spec.Suggestion {
+	var results []spec.Suggestion
 	for _, env := range os.Environ() {
 		parts := strings.SplitN(env, "=", 2)
 		name := parts[0]
@@ -20,36 +20,36 @@ func envVarGenerator(tokens []string, _ string, _ string) []core.Suggestion {
 				val = val[:57] + "..."
 			}
 		}
-		results = append(results, core.Suggestion{Cmd: name, Desc: val})
+		results = append(results, spec.Suggestion{Cmd: name, Desc: val})
 	}
 	return results
 }
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "export",
 		Description: "set environment variable",
 		Generator:   envVarGenerator,
 	})
 
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "env",
 		Description: "print environment",
 		Generator:   envVarGenerator,
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-i", Description: "start with empty env"},
 			{Name: "-u", Description: "unset variable"},
 			{Name: "-0", Description: "null delimited"},
 		},
 	})
 
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "printenv",
 		Description: "print environment variables",
 		Generator:   envVarGenerator,
 	})
 
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "unset",
 		Description: "unset variable",
 		Generator:   envVarGenerator,