Executable documentation

[jsborjesson]

Should be possible to generate rspec tests by going through the markdown code blocks with something like:

code_block = ...
code_blocks.each do |spec|
  header         = ...
  code           = ...
  result_comment = ...
  it header do
    expect(Lasp::execute(code)).to eq Lasp::execute("'#{result_comment}")
  end
end

There are a lot of examples in there now and a quick way to check that they are correct would be very valuable.

[jsborjesson]

It might actually be better to just regenerate the documentation file than to create an actual test for it, that way if the interface does change then it would update automatically, and you still get reminded of it because the diff will change.