Merge pull request #1 from web-izmerenie/master

r7
replaced deprecated "gulp-clean" package to "del" and updated dependencies versions in package.json
removed unused package "gulp-livescript" from package.json dependencies
added support LS to front-end
added stylus support
provide "prelude-ls" library for "livefy" mode for scripts
provides "nib" mixins library for "stylus" mode for styles
support source maps for styles
added watcher for styles
refactoring of paths in styles
fixed source maps conditions for styles
styles main watcher flag support
added source maps flag for styles
added "debug" flag for scripts
refactoring of scripts tasks
watcher for scripts
refactoring of sprites tasks
fixed build callbacks for styles and scripts tasks
some refactoring for watchers and sprites tasks, removed watcher stuff from sprites (cause gulp.spritesmith throws errors not to event stream)
some little refactoring of scripts tasks