IsoCity - modifications for this site

Original: https://github.com/victorqribeiro/isocity
Commit:   c5772412d3e423318f2cf479ebdd50a2b9029d84
Author:   Victor Ribeiro (MIT, see LICENSE - unchanged)
Tiles:    Kenney (www.kenney.nl), CC0 - isometric city/building tiles from OpenGameArt

Changes:
1. index.html: removed Open Graph meta tags that pointed to the author's website
   (og:url, og:image and related tags). Nothing else changed.
2. css/main.css: reworked the layout so the whole map fits inside the embed frame:
   the tile palette is a scrolling side column (a strip above the map on portrait
   screens), palette tiles are shown at 60% size, and the canvases are centered.
3. js/main.js:
   - added fitCanvas(): scales the two canvases with CSS to fit the play area
     (re-run on window resize);
   - getPosition(): pointer coordinates are converted back to canvas pixels so
     clicks and taps still hit the right tile after scaling;
   - updateHashState(): history.replaceState instead of history.pushState, so each
     placed tile does not add an entry to the host page's Back history; the city is
     also saved to localStorage (key "isocity-map") and restored on load when the
     URL has no hash.
4. Not shipped: screenshot.png.
Tile placement, erasing and the tile set are unchanged.