Provide an edit link on all articles

An initial stab at addressing issue #11,
"Provide edit links on all articles".

I started with "(edit)" but moved to a more inviting
link text that would hopefully make sense even in plain-text
contexts.

The visual design is trying to be discreet -- it could do
with some work, especially at very small viewport widths.
Merge branch 'base' into build

* base:
  Provide an edit link on all articles