Add deprecation warning for old paths.markdown option
Extract new Markdown class to encapsulate markdown splitting and marked
consume the new Markdown facade
add deprecation warning for use of  accessor on Page
pass options to marked when compiling, rather than pseudo-static setOptions
Merge branch 'extract-facade'

* extract-facade:
  pass options to marked when compiling, rather than pseudo-static setOptions
  add deprecation warning for use of  accessor on Page
  consume the new Markdown facade
  Extract new Markdown class to encapsulate markdown splitting and marked
edge cases for #get
use _.result