ref(pkg/driver): remove pkg/driver; use cnab-go for needed logic

Gopkg.toml

@@ -57,7 +57,7 @@
 
 [[constraint]]
   name = "github.com/deislabs/cnab-go"
-  version = "v0.3.0-beta1"
+  version = "v0.3.1-beta1"
 
 [[override]]
   name = "github.com/google/go-containerregistry"

cmd/duffle/main.go

@@ -9,7 +9,6 @@ import (
 	"runtime"
 	"strings"
 
-	duffleDriver "github.com/deislabs/duffle/pkg/driver"
 	"github.com/deislabs/duffle/pkg/duffle/home"
 	"github.com/deislabs/duffle/pkg/loader"
 	"github.com/deislabs/duffle/pkg/reference"
@@ -18,6 +17,7 @@ import (
 	"github.com/deislabs/cnab-go/claim"
 	"github.com/deislabs/cnab-go/credentials"
 	"github.com/deislabs/cnab-go/driver"
+	"github.com/deislabs/cnab-go/driver/lookup"
 	"github.com/deislabs/cnab-go/utils/crud"
 	"github.com/spf13/cobra"
 )
@@ -112,7 +112,7 @@ func must(err error) {
 
 // prepareDriver prepares a driver per the user's request.
 func prepareDriver(driverName string, relMap string) (driver.Driver, error) {
-	driverImpl, err := duffleDriver.Lookup(driverName)
+	driverImpl, err := lookup.Lookup(driverName)
 	if err != nil {
 		return nil, err
 	}