Add a binaryprovider to plots so that ffmpeg works "out of the box"

[logankilpatrick]

Feature request per a conversation in the plotting slack channel. We need a binary provider so that ffmpeg can be downloaded automatically (I think). This will allow the @gif macro work work by default shown here: (2nd example) http://docs.juliaplots.org/latest/examples/gr/

According to @SimonDanisch 👍
"that's done 🙂 VideoIO comes with a binaryprovider provided binary of ffmpeg"

Please let me know if you need any other details.