Benchmarking

[Thomas Moulia]

It's nice to have reports on how performant your grammar is. This should be added as a mix task where you can specify an input file, allow stdin, or perhaps specify a function that would generate the test data as a stream of Strings.

mix neotomex.benchmark --grammar=lib/grammar.ex --target=path/to/test_data

I'll use elixir-benchmark to spawn the tests.

This needs to be done before #6 so that I can understand how it changes Neotomex's performance.