Ablity to overwrite media type

[WardPearce]

Currently media type is determined via the file extension from the source url (like so). This is helpful for most use cases, but some URLs don't include the file extension, so being able to manually define the type would be great.

[eduardoRoth]

@WardPearce , latest version lets ExoPlayer and AVPlayer handle the process of identifying the video source, so it doesn't rely on some method in the plugin.