A better Slug method

[bakanis]

Latin-ish inputs should have very stable output. All inputs are passed through an NFKD transform, and anything still in the unicode Letter and Number categories are passed through intact. Anything in the Mark or Lm/Sk categories (modifiers) are skipped, and runs of characters from any other categories are collapsed to a single hyphen.

Taken from https://github.com/extemporalgenome/slug

Output e.g

Original strings of input text

My daughter's dog
Šešios žąsys su šešiais žąsyčiais
Дру́жба дру́жбой, а слу́жба слу́жбой
循序渐进 [循序漸進]

---

revel slug output:
my-daughters-dog
eios-sys-su-eiais-syiais

---

new slug output:
my-daughter-s-dog
sesios-zasys-su-sesiais-zasyciais
дружба-дружбои-а-служба-службои
循序渐进-循序漸進

[brendensoares]

Any reason for the short s variable name? I think it would be better if we tried to use descriptive variable names. Perhaps slug would be better?

[brendensoares]

We have some questions that still need answering and I would also like to see some unit tests added before we merge this into the code base.

Because of that, I've pushed this PR back to the next release. When the above needs are met, I ask that you create a new pull request that targets the develop branch along with a dedicated feature branch on your forked repo per https://github.com/robfig/revel/blob/master/CONTRIBUTING.md#how-revel-is-developed

Thank you for your contribution thus far. Let's get this added soon!

[dmage]

For Дру́жба дру́жбой, а слу́жба слу́жбой good versions are

дружба-дружбой-а-служба-службой
druzhba-druzhboy-a-sluzhba-sluzhboy

For URLs latest is preferred (because it wouldn't be skewed by url encoding).

But дружба-дружбои-а-служба-службои is awful. й != и

[jeevatkm]

Currently this package is not exists, its been changed to golang.org/x/text/unicode/norm

[brendensoares]

@bakanis are you still interested in taking the lead on this PR or should we take it over?

[notzippy]

Suggest using this version instead https://github.com/gosimple/slug