A small fix and update to the multilingual example

Enclose `{{ .Content }}` with a `{{ if .IsPage }}` test to avoid
the "Content is not a field of struct type *hugolib.Node" error.
Thanks to @spf13 for the tip!  Fixes #366.

Also update example to Hugo v0.12 conventions:
- Convert config.yaml to config.toml to follow what
  `hugo new site /path/to/site` generates
- Rename layouts/chrome to layouts/partials
- Convert `template` calls to `partial` calls
- Add .gitignore to ignore the `public` directory
- Add README.md with pointers to discussions in issues
  to help bring newcomers up to speed with this multilingual example