Adding variables to make easier to keep track of default colors and sass
functions.
Documenting gulpfile.js
	modified:   src/index.php -> adding link
	modified:   src/js/functions.js -> adding header
	modified:   src/js/main.js -> adding header
	new file:   src/js/main/util.js -> replacing src/js/principal/util.js
	new file:   src/scss/_variables.scss -> SASS VARIABLES
	modified:   src/scss/main.scss -> Site Default styles
	new file:   src/scss/mixin.scss -> Mixin functions
	new file:   src/scss/nesting.scss -> Nesting example
	new file:   src/scss/reset.scss -> Reseting tags
	deleted:    src/js/principal/util.js -> replace by src/js/util.js