Reader#new support lambda

Conflicts:
	lib/pavlov_rss/reader.rb
Merge branch 'atom_support' into develop

Conflicts:
	lib/pavlov_rss/reader.rb
Remove #fetch
Change the argument of #initialize and change the return value of check
Add #opener and modify #initialize
Modify from item_to_json to rss_to_hash and hash_to_item
Add the spec of #rss_to_hash
Simplify specs
Simplify specs
Change " to '
Remove #new_items
Add #fetch
Remove #initialize(url_or_lambda)
Bump up to 0.0.4
Merge branch 'release-0.0.4'

Conflicts:
	Gemfile.lock
	lib/pavlov_rss/version.rb