HotCold: add color to header
HotCold: change body margin and footer text-color
HotCold: fix random() function, reply grammar, change #again to #new-game
HotCold: add styling for response id paragraph
HotCold: change id again to new-game
HotCold: refactor application.js according to mentor Morgan's suggestions

Eliminate use of global variables.

Save selectors as variables, e.g. var $response = $('#response');
    Using $ in front of variable is best practice to signify jQuery object.

Make event function clickGuess() reusable.

Place message responses into variables.

Overall code cleanup in several areas to make code elegant and easier to read.