Added nbproject/ to gitignore folder which is system for Netbeanse IDE
Added SendGrid.configure method which allows to set specific properties

  Usage:

    SendGrid.configure do |config|
      config.dummy_recipient = 'noreply@example.com'
    end

  To access property:

    SendGrid.config.dummy_recipient
Merge pull request #11 from VladimirMinchenkov/send_grid_config

Send grid config