user edit view update.
user edit & show implementation.
<pre> tag bug fix.
Merge pull request #9 from yuji-shimoda/issues/#2

Issues/#2
Logout function implementation.
Merge pull request #10 from yuji-shimoda/issues/#3

Logout function implementation.
Merge branch 'master' into issues/#6

Conflicts:
	app/controllers/users_controller.rb