add close for question
modify ability for close-question
add rspec for question's closed
do not show the question of closed
modify travis.yml
moidfy travis.yml
Merge branch 'master' into close_question

Conflicts:
	db/schema.rb
Merge pull request #141 from hlee/master

for heroku only
Merge pull request #138 from caok/close_question

Close question
Fixed #125
Merge pull request #1 from jerry134/master

#125 close question