Conflicting replacements for some languages 

I realised that there are some conflicting replacements in the Slugify class. I think these are specially the Esperanto characters, since the characters are also used in other languages. For example,

Slugify.php L:60

``` php
'ĉ' => 'c',
```

Slugify.php L:414

``` php
'ĉ' => 'cx',
```

Should we remove Esperanto or provide some switch for users to select which version they want?
