quest-layout: move jumbotron to quest.html.
quest: Fix the check answer logic, remove `answered` global variable.

Every time answer a button, modify the current_question (that in
selected_question array) directly, instead of use a temporary global
variable to store the state.
quest-layout: make horizontal layout looks better in small device
quest-layout: disable option button on screen that is too small.
Add loading animation.
quest: Add score logic, maximun to 100
Merge branch 'master' into gh-pages