Update Rails to 4.2.
Add NewRelic.
Set default heading-font-weight to 100.
Update style for StaticPagesController#builder.
Add information about contributing to project.
Remove '.css' depreciation warning.
Update style for .top-nav links.
Chop at 80 chars.
Add top-nav link to Benchmarks.

* Redirect to Ruby benchmarks for the inital hook. Rails can wait.
Add top-nav link to discussion thread.
Highlight top-nav link when targetted.
Add target '_blank' to 'discuss' link.