Update traefik dependencies (docker/docker and related) (#1823)

Update traefik dependencies (docker/docker and related)

- Update dependencies
- Fix compilation problems
- Remove vdemeester/docker-events (in docker api now)
- Remove `integration/vendor`
- Use `testImport`
- update some deps.
- regenerate the lock from scratch (after a `glide cc`)

vendor/github.com/spf13/pflag/int8.go

@@ -1,6 +1,9 @@
 package pflag
 
-import "strconv"
+import (
+	"fmt"
+	"strconv"
+)
 
 // -- int8 Value
 type int8Value int8
@@ -20,7 +23,7 @@ func (i *int8Value) Type() string {
 	return "int8"
 }
 
-func (i *int8Value) String() string { return strconv.FormatInt(int64(*i), 10) }
+func (i *int8Value) String() string { return fmt.Sprintf("%v", *i) }
 
 func int8Conv(sval string) (interface{}, error) {
 	v, err := strconv.ParseInt(sval, 0, 8)