Rebased:

Wrote section Installation

Filled section Usage

Added section Features

Wrote description of gem

Changed description

Added license

Changed few wordes in description

Changed some syntax errors

Wrote API instead api

Added screenshot

Some changes at screenshots

Made new some changes

New try to add screenshot

Added new link to screenshots

Screnshot

Another try

Added screenshot

Another screnshot
Merge pull request #2 from pftg/update_description

Added description of application to README