Updated documentation on StaticOptions.SkipLogging

closes #191
Update README.md

closes #172
Update static.go

add an expires header
Add martini.Routes service to Classic middleware.
Expose the built-in Routes middleware via the Router interface.
Merge branch 'jayrox-master'
Doco fixes from @codegangsta.
Don't set expires header if we don't set the option
Convert StaticOptions.Expires to func reference
Update static test
Merge branch 'add-routes-to-classic-middleware' of github.com:BurntSushi/martini into BurntSushi-add-routes-to-classic-middleware
Merge branch 'BurntSushi-add-routes-to-classic-middleware'
Merge pull request #198 from porjo/expires

Convert StaticOptions.Expires to func reference