Prepend http protocol

[leandroncbrito]

#8 It's not possible to convert using from-url without protocol http(s)

Added function to check if the URL has HTTP protocol and prepend it.

[fabriciojs]

Looks good! Just one comment.

[fabriciojs]

I think we don't need this check, do we?

[leandroncbrito]

If we don't have the url parameter it'll return an error in line 90 (
I can change url to "let", remove it by applying the function after url parameter validation, like this:

    // change const to let
    let url = req.query.url;
    console.log('/from-url');

    if (!url) {
        let msg = 'missing parameter: \'url\'';
        deliverJson(res, {msg, params: req.params}, 400);
        return;
    }

    let pdfFilePath;
    try {
        // call the withHttp function before send to generatePdf()
        pdfFilePath = await generatePdf(withHttp(url), req.query.media);

[leandroncbrito]

@fabriciojs
What do you think? I like this new version of code, we check url parameter once