Ease extension of Slugify class

[acelaya]

I made a few minor changes.

Changed the visibility of rules and rulesets properties to protected to allow them to be overriden or used in child classes while extending Slugify.
Maybe using a getter for the rules property would do the same job, but this was my approach.

Added a third optional param to the slufigy method with the regular expression to be applied to the string.
I made this because I needed to allow other characters in the slug, like dots for filenames. I didn't want My Cool File.zip to become my-cool-file-zip but my-cool-file.zip.
I wasn't sure if that argument should be set in the constructor or in this method, but I think this is good enough.

I was thinking also on giving the option to define if the string should be lowered or not, but I'm not sure what's the best way to do that.

[coveralls]

Coverage remained the same when pulling 6e365df on acelaya:feature/protected-properties into 56b8981 on cocur:master.

[florianeckerstorfer]

First you should split this up into two Pull Requests. These are completely different things.

I will merge the PR to change the visibility of the properties, but I don't think it is useful to change the interface of slugify(). If you want file names in the way you want them, you should remove the extension before passing the name to slugify and add it back later.

[acelaya]

You are right, this should be split into two pull requests. I'll do it right away.
About changing the interface specification (which I indeed forget, I just updated the concrete class), probably making properties protected will ease customize the regular expression by extending the Slugify class.

[acelaya]

Done, just removed the last commit and pushed it again (with --force)

[coveralls]

Coverage remained the same when pulling 0230408 on acelaya:feature/protected-properties into 56b8981 on cocur:master.

[florianeckerstorfer]

Regarding the regular expression. If there is need to modify it, there should be another way than supplying another parameter to slugify(). I would suggest making the regular expression a property. Either we supply a setter method or we extend the Slugify class if we need a different regexp.

[acelaya]

Yes, I like the idea of using a property. A protected property could be overriden, but maybe a setter would be good too.
I'm even thinking on providing a constructor with the regular expression as an optional argument with the current regular expression as the default value.
If you like the idea I'll make another pull request.

[florianeckerstorfer]

Yes, please make another PR. Thanks.