Added feature that allows for truncating the post body on the home page at a
user defined point in the text.

Conflicts:

	app/views/admin/posts/_form.html.erb
	app/views/posts/index.html.erb
Fix truncate-home-page-posts specs

Two specs were failing:

* The length of a truncated post has changed, so adjust the
  spec to check content rather than just length, so it would show a more
  meaningful failure message, and so it passes now

* The post_path helper was not available, so include the module that
  supplies it