Update pelican config file for pelican v3.5

- ignore `cache` dir.
- set `static paths` for `{attach}`.
Upgrade Foundation to 5.4.7 and typo.css to commit/40b78e7

- update app.css overrides for Foundation `code` style.
Add margin-bottom css for image display.
Add new writings article: rbenv-pyenv-#1-init.rst