Replace godep with vndr

Vndr has a simpler configuration and allows pointing to forked
packages. Additionally other docker projects are now using
vndr making vendoring in distribution more consistent.

Updates letsencrypt to use fork.
No longer uses sub-vendored packages.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

vendor/github.com/garyburd/redigo/internal/commandinfo.go

@@ -12,7 +12,7 @@
 // License for the specific language governing permissions and limitations
 // under the License.
 
-package internal
+package internal // import "github.com/garyburd/redigo/internal"
 
 import (
 	"strings"

vendor/github.com/garyburd/redigo/redis/doc.go

@@ -166,4 +166,4 @@
 //   if _, err := redis.Scan(reply, &value1, &value2); err != nil {
 //      // handle error
 //  }
-package redis
+package redis // import "github.com/garyburd/redigo/redis"