vendor: update

vendor/github.com/pkg/errors/.travis.yml

@@ -1,11 +1,10 @@
 language: go
 go_import_path: github.com/pkg/errors
 go:
-  - 1.4.x
-  - 1.5.x
-  - 1.6.x
-  - 1.7.x
-  - 1.8.x
+  - 1.4.3
+  - 1.5.4
+  - 1.6.2
+  - 1.7.1
   - tip
 
 script:

vendor/github.com/pkg/errors/stack.go

@@ -79,14 +79,6 @@ func (f Frame) Format(s fmt.State, verb rune) {
 // StackTrace is stack of Frames from innermost (newest) to outermost (oldest).
 type StackTrace []Frame
 
-// Format formats the stack of Frames according to the fmt.Formatter interface.
-//
-//    %s	lists source files for each Frame in the stack
-//    %v	lists the source file and line number for each Frame in the stack
-//
-// Format accepts flags that alter the printing of some verbs, as follows:
-//
-//    %+v   Prints filename, function, and line number for each Frame in the stack.
 func (st StackTrace) Format(s fmt.State, verb rune) {
 	switch verb {
 	case 'v':