lib/main.js
function normalizeSlug(slug) {
    if(typeof slug !== 'string') throw new Error('slug must be a string');
    if(slug === '') throw new Error('slug cannot be an empty string');
    if(isNaN(Number(slug))) return slug;
    slug = slug.replace(/^(0+)/, '').trim();
    while(slug.length < 2) {
        slug = '0' + slug;
    }
    return slug;
}
function normalizeSlug(slug) {
    if(typeof slug !== 'string') throw new Error('slug must be a string');
    if(slug === '') throw new Error('slug cannot be an empty string');
    if(isNaN(Number(slug))) return slug;
    slug = slug.replace(/^(0+)/, '').trim();
    while(slug.length < 2) {
        slug = '0' + slug;
    }
    return slug;
}
Pads a slug to 2 significant digits.
Examples:
'1'    -> '01'
'001'  -> '01'
'12'   -> '12'
'123'  -> '123'
'0123' -> '123'
Words are not padded:
'a' -> 'a'
'0word' -> '0word'
And as a matter of consistency:
'0'  -> '00'
'00' -> '00'

@param slug
@returns {*}