[+]: use "voku/portable-ascii"

[voku]

reference: #51

Here I added "voku/portable-ascii" which is for example used in the "dev-master" version of laravel and it's also based on this project. 😄

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I know it's not that easy to pick a minimal php version to support, but most systems has already upgraded to > 7.0 (https://blog.packagist.com/php-versions-stats-2019-1-edition/) so maybe it's time to move forward?

Linux Distro	Version	End of Life	Default PHP
Ubuntu	14.04 (Trusty)	April 2019 (EOL)	5.5.9
Ubuntu	16.04 (Xenial)	April 2024	7.0
Ubuntu	18.04 (Bionic)	April 2028	7.2
Debian	8 (Jessie)	June 30, 2020	5.6.29
Debian	9 (Stretch)	~2022	7.0
Fedora	29	October 30, 2018	7.2.10
Fedora	30	April 30, 2019	7.3.4
OpenSUSE	Leap 15.1	November 22, 2020	7.2.5
CentOS	6	November 30, 2020	5.3.3
CentOS	7	June 30, 2024	5.4.16
RHEL	6	November 30, 2020	5.3.3
RHEL	7	June 30, 2024	5.4.16
RHEL	8	May 2029	7.2
OEL	6	March 2021	7.0 (min)
OEL	7	July 2024	7.0 (min)

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PS: in my fork I also added different "stop-words" (https://github.com/voku/stop-words/tree/master/src/voku/helper/stopwords) for different languages and some other specials like support for currencies (https://github.com/voku/urlify/blob/master/src/voku/helper/URLify.php#L484). I don't know if this is also interesting for you?

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This change is 

[jbroadway]

Thanks, this is great!

I updated the travis config to be PHP 7.0+ now - it's been some time since even that version of PHP was technically supported! I ran phpunit locally so I don't think we need to wait on travis succeeding to merge this, since it should end up green on master anyway.

And yes, I'm definitely interested in language-specific stopwords and currency handling. Assuming an English-only stopword list that people are unlikely to change was always a weak point in the library.