vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

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

@@ -196,6 +196,7 @@ func TestWithMessage(t *testing.T) {
 			t.Errorf("WithMessage(%v, %q): got: %q, want %q", tt.err, tt.message, got, tt.want)
 		}
 	}
+
 }
 
 // errors.New, etc values are not expected to be compared by value