Merge pull request #4 from bchretien/master

Update benchmark with PaGMO and NLopt.
_layouts/default.html: update Google Analytics tracker
benchmark.html: add button to download the graph
Add Disqus support
Enable MathJax only when necessary
Enable Disqus on selected pages
Add OAuth support
development.html: log more data
development.html: fix typo
development.html: only log info if an error occurs
development.html: improve page layout
Fix style in benchmark.