Magic Overhaul

[n1073645]

An overhaul of the magic operation.

It's to extend the functionality of Magic by adding the following to each operation, where appropriate:

- More input criteria.
- More output criteria.
- Entropy of the input data and output data.
- Some mime-checking of operations that return files.
- Then some extra ones that don't fit into any of the above.

[d98762625]

You've changed the return behaviour of this function, please update the function doc comment to reflect this. (I know this is WIP)

[d98762625]

This in operator usage looks way cleaner than the Object.prototype.hasOwnProperty.call(object, key) call. Please just do a mental check each time you use it to make sure you won't be hitting on something up the object's prototype chain. See inherited properties here for more info. (I can't see any bad uses here)

[n1474335]

Currently reviewing this and making some changes. Don't push any more updates.

[n1474335]

Really good stuff @n1073645. I made some changes to improve performance, simplify markup and get better test coverage. Take a look here: b765534

Very happy that we can detect deflated data without any headers - that's a nice addition.