Add flag for forcing lowercase slugs

[jaketrent]

Added flag for forcing lowercase slugs.

Syntax:

slug('FOO-Bar-baZ', true)
# or
slug('FOO-Bar-baZ', '_', true)

And added tests to match. All passing.

[thom4parisot]

It would be better to keep the second argument as:

• a String for a seperator shortcut
• an Object containing options, like the following:

slug("My String", { lowerCase: true, separator: '_', … });

Otherwise you end up with implicit arguments, making any further extension complicated.

[dodo]

@oncletom thats how it's implemented. but in the end i removed the lowerCase option since slug('str', {…}).toLowerCase() is less code and same result.

[thom4parisot]

:+1: