Extend README with a Dynamic Facebook Pixel Options example

[simonknoll]

Would it be possible to add an example on how to use the following feature
#101
I've tried to take advantage of this feature but I keep failing. How should the lambda be passed to the config/initializer?

[bumi]

what did you try?

maybe these examples help:
user id example for google: https://github.com/railslove/rack-tracker#google-analytics
in the test: https://github.com/railslove/rack-tracker/blob/master/spec/handler/facebook_pixel_spec.rb#L24

but indeed an example - simar to the ones for the other trackers - would be helpful. maybe I can help you get it running and you can make a pull request for that?

[simonknoll]

I managed to get it working. Thanks. I've created a pull request.

[bumi]

awesome, happy to hear that it worked and thanks for the pull request to improve the readme on this.
I will look at it tomorrow.