Switch from yargs to minimist

For our simple usecase we do not need the extra functionality of yargs.
This removes 4 dependencies from our dependency graph.

https://github.com/bcoe/yargs
https://github.com/substack/minimist

gulpfile.js

@@ -1,7 +1,7 @@
 // ## Globals
 /*global $:true*/
 var $           = require('gulp-load-plugins')();
-var argv        = require('yargs').argv;
+var argv        = require('minimist')(process.argv.slice(2));
 var browserSync = require('browser-sync');
 var gulp        = require('gulp');
 var lazypipe    = require('lazypipe');