feat(stylus): add stylus support

Add Stylus in techs and prompts

Include gulp-stylus module in package

Add stylus files in templates

Add stylus logo

Add gulp-stylus' task

Add __bootstrap-vendor.styl

Fix path to bootstrap.css

Remove unnecessary files

Add gulp-stylus to test's npm dependencies

Remove unnecessary params to gulp-stylus' task

vendorStylesPrep... is false if Stylus is selected