Look through a directory for markdown files and add them as posts.

def add_posts(self, path='posts'):
		"""
		Look through a directory for markdown files and add them as posts.
		"""
		path = os.path.join(self.root_path, path)
		self.cm.add_posts([
			self.cm.Post.from_file(file)
			for file in _listfiles(path)
		])