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/cc/cmake.go

@@ -1,14 +1,14 @@
 package cc
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "cmake",
 		Description: "Command-line interface of the cross-platform buildsystem generator CMake",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "permissions", Description: "Format: <u=rwx,g=rx,o=rx>"},
 			{Name: "cat", Description: "Concatenate files and print on the standard output"},
 			{Name: "chdir", Description: "Change the current working directory and run a command"},
@@ -37,7 +37,7 @@ func init() {
 			{Name: "time", Description: "Run command and display elapsed time"},
 			{Name: "true", Description: "Do nothing, with an exit code of 0"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--build", Description: "Use a build preset to specify build options"},
 			{Name: "--list-presets", Description: "For multi-configuration tools, choose configuration <cfg>"},
 			{Name: "--clean-first", Description: "Build target clean first, then build"},