Move the code examples to a non-package directory.

Code examples are intended for direct inspection by the end user, not
for import as modules from the distribution. Move the code examples to a
separate top-level ‘examples/’ directory.

diff --git a/xkcdpass/example_import.py b/examples/example_import.py
similarity index 100%
rename from xkcdpass/example_import.py
rename to examples/example_import.py

diff --git a/xkcdpass/example_json.py b/examples/example_json.py
similarity index 100%
rename from xkcdpass/example_json.py
rename to examples/example_json.py