taskpaper: rename file to proper extension

gendates.go

@@ -21,7 +21,7 @@ var tplMap = map[string]string{
 	"assignments": "assignments.adoc.tpl",
 	"schedule":    "schedule.adoc.tpl",
 	"syllabus":    "syllabus.adoc.tpl",
-	"course":      "course.task.tpl",
+	"course":      "course.taskpaper.tpl",
 }
 
 type DayMap map[int]time.Time
@@ -145,7 +145,7 @@ func main() {
 }
 
 func writeTaskPaper(c Config) error {
-	f, err := os.Create("course.task")
+	f, err := os.Create("course.taskpaper")
 	defer f.Close()
 	if err != nil {
 		return err