Added 'check' function to gulp, which use jsHint

Installed gulp-jshint
Added 'check function'
Js files are validated according to idiomatic.js
Add style checking feature to gulp

Install gulp-jshint that provide possibility to check some properties of js files.
It is ready in node_modules/.bin  with `gulp check` command.
Separately there is a .jshtinrc file which contains the aspects of checking.
Js files are already checked, passed the test.