Specify left: 0; for tooltips

Otherwise Firefox is a little confused.
Jekyll build

jekyll 1.2.1
Darwin Pseudonym.local 13.1.0 Darwin Kernel Version 13.1.0: Thu Jan 16 19:40:37 PST 2014; root:xnu-2422.90.20~2/RELEASE_X86_64 x86_64

Configuration file: /Users/jmah/Documents/Streams/dev-etc/_config.yml
            Source: /Users/jmah/Documents/Streams/dev-etc
       Destination: /Users/jmah/Documents/Streams/dev-etc/_site
      Generating... Configuration file: /Users/jmah/Documents/Streams/dev-etc/_config.yml
done.