Add options structure

[GustavoCaso]

Fixes #34

Is not all options added but I wanted to share the structure before adding all of them since they are a lot 💥

So far I mostly copy the logic from https://github.com/talklittle/ffmpex. Thanks @talklittle

If people are ok the structure I will add the rest of the options 😄

Also, another thing we could think about is deprecating custom method in the future once this is merged.

[GustavoCaso]

@talklittle, @uesteibar I have added the requested changes. Once we are happy with the changes is just a matter of including all the options and improve the documentation.

[talklittle]

Looks great! Thank you very much for working on this @GustavoCaso ! And thanks @uesteibar for reviewing.