Changed phrasing of questions and tidied up typos.

Changed the phrasing of the questions within the array. Also removed a
question mark inadvertently added to the end of an option in the array.
Additional Comments to quiz.js

Added additional comments to quiz.js to make clearer the steps in the
javascript functions.
Update index.html
Merge pull request #5 from sunilunka/gh-pages

Added titles (tooltips) and 'alt' text for buttons and images.