Create Acid test for liquid compatibility

[epage]

The liquid test suite has helped us identify a lot of gaps in our compatibility but it is very incomplete still.

Ideas

• Create common input for liquid-rust and liquid-ruby and verify outputs
• Easy to test variety of corner cases (e.g. nil, empty, and blank or unexpected data types)

[epage]

One tricky thing will be to separate implementation concepts, bugs in liquid-ruby, and bugs in liquid-rust.

For example {{ 5.size }} in the Ruby implementation returns how many bytes 5 takes up in-memory.