Fix Mobile Images, Alternate Images with CSS

[ryanbaer]

Hey, great port of the theme! Appreciate you bringing it to Hugo.

I noticed a few things when working with it, mainly that images became "squashed" on the mobile view:

This PR contains a fix for that issue, as well as:

• Simplify loop in partials/portfolio.html: the images are now alternated left and right via CSS, compared to the previous approach using the Go template loop with mod 2. As a result, the template file is now cleaner and roughly half the size.
• Improve the hover transitions in partials/portfoilio.html: Referencing the original theme, the image remains hidden outside the bounds of the box when zooming, so this theme now does that as well. Additionally, hovering over anywhere on the row now zooms the image and highlights the text as in the original theme.
• Adjust sidebar on mobile in `_default/single.html: this section now takes up less screen real estate on mobile, keeping the tags inline under their respective headings of Categories and Tags
• Other minor CSS tweaks, mostly for mobile / tablet view

Check it out and let me know what you think.

[ageekymonk]

Thanks a lot for the pull request. Meged it