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/runner/dbt.go

@@ -1,14 +1,14 @@
 package runner
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "dbt",
 		Description: "CLI for dbt - Data Build Tool",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "build", Description: "Run models, test tests, snapshot snapshots, and seed seeds"},
 			{Name: "directory", Description: "Directory containing profiles.yml"},
 			{Name: "name", Description: "Name of profile to use when running dbt project"},
@@ -45,7 +45,7 @@ func init() {
 			{Name: "ls", Description: "Lists resources defined in a dbt project"},
 			{Name: "parse", Description: "Parse dbt project and write detailed timing information"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--full-refresh", Description: "Treat incremental models as table models"},
 			{Name: "-x", Description: "Exit immediately if a single model fails to build"},
 			{Name: "--profiles-dir", Description: "Set the profiles directory"},