README: update default collation to utf8mb4_general_ci (#1054)

Author: julienschmidt

README.md

@@ -463,13 +463,13 @@ Alternatively you can use the [`NullTime`](https://godoc.org/github.com/go-sql-d
 
 
 ### Unicode support
-Since version 1.1 Go-MySQL-Driver automatically uses the collation `utf8_general_ci` by default.
+Since version 1.5 Go-MySQL-Driver automatically uses the collation ` utf8mb4_general_ci` by default.
 
 Other collations / charsets can be set using the [`collation`](#collation) DSN parameter.
 
 Version 1.0 of the driver recommended adding `&charset=utf8` (alias for `SET NAMES utf8`) to the DSN to enable proper UTF-8 support. This is not necessary anymore. The [`collation`](#collation) parameter should be preferred to set another collation / charset than the default.
 
-See http://dev.mysql.com/doc/refman/5.7/en/charset-unicode.html for more details on MySQL's Unicode support.
+See http://dev.mysql.com/doc/refman/8.0/en/charset-unicode.html for more details on MySQL's Unicode support.
 
 ## Testing / Development
 To run the driver tests you may need to adjust the configuration. See the [Testing Wiki-Page](https://github.com/go-sql-driver/mysql/wiki/Testing "Testing") for details.