Fix goreportcard issues (#271)

* Fixed misspell

* Fixed ineffassign

`user` and `password` always got overwritten
`orderedVals` was initialized with an empty array but always got overwritten by either `sortByLines()` or `sortAlphabetical`
`err` was assigned a `nil` value that was either overwritten or unused anyways

* Fix comment for DeletePath

The comment assumed the method was named Delete, i guess a rename happened at some point

* Update doc_test.go

doc_test.go

@@ -16,13 +16,14 @@ func Example_tree() {
 		fmt.Println("Error ", err.Error())
 	} else {
 		// retrieve data directly
-		user := config.Get("postgres.user").(string)
-		password := config.Get("postgres.password").(string)
+		directUser := config.Get("postgres.user").(string)
+		directPassword := config.Get("postgres.password").(string)
+		fmt.Println("User is", directUser, " and password is", directPassword)
 
 		// or using an intermediate object
 		configTree := config.Get("postgres").(*toml.Tree)
-		user = configTree.Get("user").(string)
-		password = configTree.Get("password").(string)
+		user := configTree.Get("user").(string)
+		password := configTree.Get("password").(string)
 		fmt.Println("User is", user, " and password is", password)
 
 		// show where elements are in the file

keysparsing_test.go

@@ -24,7 +24,7 @@ func testResult(t *testing.T, key string, expected []string) {
 func testError(t *testing.T, key string, expectedError string) {
 	res, err := parseKey(key)
 	if err == nil {
-		t.Fatalf("Expected error, but succesfully parsed key %s", res)
+		t.Fatalf("Expected error, but successfully parsed key %s", res)
 	}
 	if fmt.Sprintf("%s", err) != expectedError {
 		t.Fatalf("Expected error \"%s\", but got \"%s\".", expectedError, err)

marshal.go

@@ -546,8 +546,8 @@ func (d *Decoder) valueFromTree(mtype reflect.Type, tval *Tree) (reflect.Value,
 
 				if !found && opts.defaultValue != "" {
 					mvalf := mval.Field(i)
-					var val interface{} = nil
-					var err error = nil
+					var val interface{}
+					var err error
 					switch mvalf.Kind() {
 					case reflect.Bool:
 						val, err = strconv.ParseBool(opts.defaultValue)

toml.go

@@ -275,7 +275,7 @@ func (t *Tree) Delete(key string) error {
 	return t.DeletePath(keys)
 }
 
-// Delete removes a key from the tree.
+// DeletePath removes a key from the tree.
 // Keys is an array of path elements (e.g. {"a","b","c"}).
 func (t *Tree) DeletePath(keys []string) error {
 	keyLen := len(keys)

tomltree_write.go

@@ -259,7 +259,7 @@ func (t *Tree) writeTo(w io.Writer, indent, keyspace string, bytesCount int64, a
 }
 
 func (t *Tree) writeToOrdered(w io.Writer, indent, keyspace string, bytesCount int64, arraysOneElementPerLine bool, ord marshalOrder) (int64, error) {
-	orderedVals := make([]sortNode, 0)
+	var orderedVals []sortNode
 
 	switch ord {
 	case OrderPreserve: