Rename user_signed_in to user_logged_in
Redo header & nav authentication controls

* Add ids to links
* Replace ugly unless x … if … with an if … else …
Fix error when there is no accept language in the request
Remove created_at method

(It seems it is already a time interval, no need to parse it)
Add meta charset utf8 to layout
Add ids to several submit buttons & links
Add comments which shows the pages in a browser on error
click_on instead of click_link + click_button. Use ids when conflict
Add should_see_selector helpers
use should_see_selector helpers instead of looking for text
Remove "should see Logout" in a couple specs
click_link -> click_on
English
Merge branch 'travis' into green
use ids instead of strings to attempt to fix spec in travis
Merge pull request #17 from madridrb/green

Make it Green