shell auto-completion via tab for saved bookmarks

[sassman]

As a user I want to have auto-completion for my bookmarks So that I save typing time and brain memory capacity

# given this bookmark
curlz r --bookmark-as gitignore 'https://api.github.com/gitignore/templates/{{ prompt_for("Language") | title }}'

# when hitting <TAB> here: 
curlz r gi<TAB>

# it will expand to the bookmark:
curlz r gitignore