Various improvements and optimizations

[DCNick3]

Relative urls are more flexible, so absolute ones were replaced with them.

Greatly improved browser support by replacing lamdas with classic function definition.

Replaced css modification to hiding or showing image with css classes, which has less overhead.

Removed unnecessary css libraries, which created 2 additional requests to external sites.

[caguiclajmg]

Looks good, minor nitpicks:

• The noscript message, Please enable JavaScript execution in your browser
• In show_image,

function show_image(index) {
    for (var i = 0; i < images.length; ++i)
        images[i].className = (i === index) ? "container" : "hidden container"; // or its equivalent if-style
}

[DCNick3]

Looks sane

[caguiclajmg]

Sane enough, merging.