extract Category class out of template into lib class
Pages needs a reference to 'site' for templating
create categories at wrapper level, not index body

to facilitate reuse for table of contents/navigation
Use site.categories to generate navigation/ToC
Specify category title explicitly and derive the slug (not vice/versa)
Move pages to match category slug
Underscore templates ought to be escaping HTML entities
extract Topic class
Refactor Topic
Page template requires slug anyhow.
Don't touch .attributes directly
Just use page itself
don't need Topic at all
update grunt-markdown-blog to fix html escaping
Merge branch 'lib'

* lib:
  update grunt-markdown-blog to fix html escaping
  don't need Topic at all
  Just use page itself
  Don't touch .attributes directly
  Page template requires slug anyhow.
  Refactor Topic
  extract Topic class
  Underscore templates ought to be escaping HTML entities
  Move pages to match category slug
  Specify category title explicitly and derive the slug (not vice/versa)
  Use site.categories to generate navigation/ToC
  create categories at wrapper level, not index body
  Pages needs a reference to 'site' for templating
  extract Category class out of template into lib class