Char generator

This can get enormously complicated, with latin1 in UTF-8 and non-Latin characters.
As a first implementation I propose ASCII (0-127) and printable ASCII (32-127) chars.
I don’t understand the meaning of this test. All [basic-latin](http://unicode-table.com/en/blocks/basic-latin/) code points are printable except for `U+007F`. So this test should be called maybe `testPrintableCharacters` and the assertion should be something like
```php
$this->assertNotEquals(127, ord($char));
```
?