Trim trailing spaces and convert tabs to spaces.
Add .gitignore.
Loesslessly compress images.

Before: 1,10 MB (1.157.755 bytes)
After:  1,08 MB (1.141.968 bytes)
Remove double backslash.
Add robots.txt and sitemap.xml.
Improve feed.xml.
Re-indent _config.yml and exclude README.
Tweak relative URLs.
Minor css tweaks.