Merge pull request #9 from catherinev/create_authentication_login_logout

Create authentication login logout
add question controller
merge conflict fixed
create view for signin page
failed signin does what it needs to
add error message and style
add SessionsHelper, signin should work once QuestionsController exists
Merge pull request #10 from catherinev/questions

Questions
create logout functionality, needs QuestionsController
fixed application conflict, kept version with current_user argument