Remove smart tabs option and trailing option

They have been removed from JSHint v2.5.0.

https://github.com/jshint/jshint/releases/tag/2.5.0
Update imagemin-gifsicle and imagemin-optipng
Update URL of imagemin-app

https://github.com/imagemin/imagemin-app
Merge pull request #52 from shinnn/master

Bump deps / Update .jshintrc and readme