Fix #673 comment shape compatibility issue with the recent Excel versions

* Fix comment shape compatibility issue

* Using Go modules with Travis CI

* Update .travis.yml
Co-authored-by: Canh Nguyen <nguyenxc@seagroup.com>
Co-authored-by: xuri <xuri.me@gmail.com>

.travis.yml

@@ -19,8 +19,8 @@ env:
     - GOARCH=386
 
 script:
-  - go vet ./...
-  - go test ./... -v -coverprofile=coverage.txt -covermode=atomic
+  - env GO111MODULE=on go vet ./...
+  - env GO111MODULE=on go test ./... -v -coverprofile=coverage.txt -covermode=atomic
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)

comment.go

@@ -164,7 +164,7 @@ func (f *File) addDrawingVML(commentID int, drawingVML, cell string, lineCount,
 				},
 				VPath: &vPath{
 					Gradientshapeok: "t",
-					Connecttype:     "miter",
+					Connecttype:     "rect",
 				},
 			},
 		}