Feature release v1.1.0.

New features:

• Markdown parser can now create entry previews. Simply include <​!– more –> in the text of an entry and use the :preview key instead of :contents.
• Text substitution middleware (substitute) with optional Clojure evaluation (substitute-by) - use {​{key-name-or-Clojure-code}} in your entries, and substitution middleware will... Substitute it for you. Yay?