Display "file size" by default.

This is generally the preferred view of the data and makes
a more sensible default.

Have also added a "mode" option for switching the default
view: mostly because the demo looks nicer on first glance
using the previous one :)

Fixes #14.
Re-introduce the --open CLI flag.

Until node-bcat or an equivalent tool supports piping in HTML pages,
this provides a quick and easy means for just opening disc straight
away and seeing the results.

See also: #12
1.1.0