introduce interface for data fetching

[tonybart1337]

In order to use this library in our application we would need a way to fetch data from a remote.
I like the way you patched it here, which means that it should be relatively easy to do

I would like to propose some kind of interface that a user will be able to pass to the instance of a demuxer, so when we call load or any other function it will use that interface to fetch the data. Caching can also be implemented into the interface as well

[ForeverSc]

Yep, I have the same idea. This has been discussed at #11 (comment). I need some spare time to design how to add the interface. If you have better ideas, you’re welcome to submit a pull request. :)