Property keys are now imported as components

Property keys weren't being imported as components so I went and looked at the source, and it seemed you assumed some "components" key, instead of simply iterating over an object. Perhaps it was an old version of Tiled, or I misunderstood which properties the library imports.

Regardless, my change takes all the properties' keys and adds them as components.
It was enough to make my code work =P

Cheers,

Jason