Write screenshot to file

[negiDharmendra]

• Changed default screenshot grabber to write to file and return file path.
• Depricate existing custom screenshot grabber API contract.
• Create a new API contact for custom screenshot grabber to write the screenshot into file and returning file path instead of screenhsot bytes.

Gauge.configure do |config|
  config.custom_screenshot_writer = -> {
    screenshot_data = driver.screenshot_as(:png)
    file = File.join(config.screenshot_dir, 'screenshot-name.png')
    File.write(file, screenshot_data)
    File.basename(file)
  }
end