Prevent duplicate load path entries.

Fixes #1729.
[#1733] clarify that RSpec.reset resets all user configuration

And users are responsible for re-configuration
[#1733] fix typo "they use runner" -> "they use the runner"
Merge pull request #1736 from waterlink/1733_improve_yard_docs_for_rspec_reset

Clarify that RSpec.reset resets all user configuration
Merge pull request #1735 from rspec/fix-1729

Prevent duplicate load path entries.
Fix regression in rake task pattern handling.

Since our change to forward `task.pattern` to `rspec`
in #1653, it has not handled patterns that are relative
to the current directory for a side directory (e.g.
not under `spec`) of specs. This restores that behavior.

Fixes #1728.