Use a single line for slice encoding (#119)

parser_test.go

diff --git a/parser_test.go b/parser_test.go
index 8fab905..7769da3 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -646,7 +646,7 @@
 		{time.Date(1979, time.May, 27, 7, 32, 0, 0, time.UTC),
 			"1979-05-27T07:32:00Z"},
 		{[]interface{}{"gamma", "delta"},
-			"[\n  \"gamma\",\n  \"delta\",\n]"},
+			"[\"gamma\",\"delta\"]"},
 		{nil, ""},
 	} {
 		result := toTomlValue(item.Value, 0)

tomltree_conversions.go

diff --git a/tomltree_conversions.go b/tomltree_conversions.go
index aff8fe7..db3da0d 100644
--- a/tomltree_conversions.go
+++ b/tomltree_conversions.go
@@ -79,11 +79,11 @@
 	case time.Time:
 		return tab + value.Format(time.RFC3339)
 	case []interface{}:
-		result := tab + "[\n"
+		values := []string{}
 		for _, item := range value {
-			result += toTomlValue(item, indent+2) + ",\n"
+			values = append(values, toTomlValue(item, 0))
 		}
-		return result + tab + "]"
+		return "[" + strings.Join(values, ",") + "]"
 	case nil:
 		return ""
 	default: