Improve Wikilinks

[KnowledgeGarden]

This might render the issue related to adding Wikilinks to medium.js moot.
Firstly,

• Wikilinks require validation - it's possible to make a typo and do [[foo[[ instead of [[foo]] and related typos

• A wikilink button for highlighted text seems far more important than a rich text editor bar at this time.
  This all implies something like

• Remove medium.js entirely

• Write a keystroke event which detects a highlighted span and then enables a Wikilink button to take care of making those links