Revise file names and dir layout for issue 360

You can of course preview this new layout yourself by visiting: https://github.com/pnkfelix/rfcs/tree/fsk-revise-file-names-and-dir-layout-for-issue-360

See associated discussion from weekly meeting: https://github.com/rust-lang/meeting-minutes/blob/master/weekly-meetings/2014-10-07.md#how-to-link-to-rfcs

Fix #360.