do not force the permalink to be a dir if it ends on .html

Fixes #798.
test per-post permalinks

Add tests for setting a permalink on a post (in YAML frontmatter),
both the "old way" (generating an index.html) and with an .html ex-
tension.
Merge branch 'permalink-no-dir' of git://github.com/maul-esel/jekyll into maul-esel-permalink-no-dir

* 'permalink-no-dir' of git://github.com/maul-esel/jekyll:
  test per-post permalinks
  do not force the permalink to be a dir if it ends on .html

Conflicts:
	features/step_definitions/jekyll_steps.rb
Fix date format in permalink.features.