add haml-rails gem
refactor Gemfile
separate lines in README
extract factory girl sequences to separate file
add sequences for comment attributes

Conflicts:
	test/factories/sequences.rb
add attributes to comments factory
add comment creation to posts factory
add post creation to posts#index test
add /config/spring.rb to .gitignore
refactor comments#create test
refactor comments#destroy test
refactor posts#create test
refactor posts#update test
remove FIXME comment for posts#create test