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/string.go

@@ -1,5 +1,7 @@
 package pflag
 
+import "fmt"
+
 // -- string Value
 type stringValue string
 
@@ -16,7 +18,7 @@ func (s *stringValue) Type() string {
 	return "string"
 }
 
-func (s *stringValue) String() string { return string(*s) }
+func (s *stringValue) String() string { return fmt.Sprintf("%s", *s) }
 
 func stringConv(sval string) (interface{}, error) {
 	return sval, nil