Code Review: Done

Hey Markus,

Everything nice over here, too :+1: 
I especially like that you present a nice example, makes it much easier to get into it. End user friendly!

Again, made some tweaks to the README, TODO, gemspec and comments. No code changed. A few questions:


## Logging in the Example
When I switch from stderr to stdout I still see no output. What am I doing wrong?

## Private API?
Why are almost all APIs private? Only in the gateway there are some public ones. Is this the only thing public?

## Nested classes

The same question like in the other repo, but to the power of 5: Nested classes. Nested classes that are declared private oO
Examples can be found here `lib/veritas/adapter/arango/visitor/for/binary/join.rb` and here `lib/veritas/adapter/arango/visitor/for/binary/product.rb`.