graph/formats/dot,travis: update gocc version

.travis.yml

@@ -43,7 +43,7 @@ before_install:
  - go get golang.org/x/tools/cmd/cover
  - go get github.com/mattn/goveralls
  # Required for dot parser checks.
- - ./.travis/install-gocc.sh 0e2cfc030005b281b2e5a2de04fa7fe1d5063722
+ - ./.travis/install-gocc.sh 66c61e91b3657c517a6f89d2837d370e61fb9430
 
 addons:
   apt:

graph/formats/dot/internal/errors/errors.go

@@ -13,8 +13,8 @@
 package errors
 
 import (
-	"bytes"
 	"fmt"
+	"strings"
 
 	"gonum.org/v1/gonum/graph/formats/dot/internal/token"
 )
@@ -31,7 +31,7 @@ type Error struct {
 }
 
 func (e *Error) String() string {
-	w := new(bytes.Buffer)
+	w := new(strings.Builder)
 	fmt.Fprintf(w, "Error")
 	if e.Err != nil {
 		fmt.Fprintf(w, " %s\n", e.Err)
@@ -52,7 +52,7 @@ func (e *Error) String() string {
 }
 
 func (e *Error) Error() string {
-	w := new(bytes.Buffer)
+	w := new(strings.Builder)
 	fmt.Fprintf(w, "Error in S%d: %s, %s", e.StackTop, token.TokMap.TokenString(e.ErrorToken), e.ErrorToken.Pos.String())
 	if e.Err != nil {
 		fmt.Fprintf(w, ": %+v", e.Err)

graph/formats/dot/internal/parser/parser.go

@@ -13,8 +13,8 @@
 package parser
 
 import (
-	"bytes"
 	"fmt"
+	"strings"
 
 	parseError "gonum.org/v1/gonum/graph/formats/dot/internal/errors"
 	"gonum.org/v1/gonum/graph/formats/dot/internal/token"
@@ -76,7 +76,7 @@ func (s *stack) popN(items int) []Attrib {
 }
 
 func (s *stack) String() string {
-	w := new(bytes.Buffer)
+	w := new(strings.Builder)
 	fmt.Fprintf(w, "stack:\n")
 	for i, st := range s.state {
 		fmt.Fprintf(w, "\t%d: %d , ", i, st)