A simple file loader demo of
[Perspective](https://github.com/perspective-dev/perspective). The given
CSV/Feather must be in a form Perspective's `Table()` constructor supports:

- First row must be column names.
- Subsequent rows should be mono-typed (but if not you will just get `string`
  columns and you'll need to use ExprTK expressions to cast).
- Well-formed (Consistent # of `,` per line, strings should be quoted,
  especially if they contain `,` themselves).

This example does not have a server component, all
calculation/loading/manipulation of the data is done in the browser, and the
data "uploaded" never leaves your browser/computer.
