Add varenc/ffmpeg to list of interesting taps

[alebcay]

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It would be helpful to include this link in the list for users that wish to have custom-built versions of ffmpeg, especially with nonfree features enabled (which Homebrew cannot distribute), such as --with-fdk-aac.

[zbeekman]

LGTM

[zbeekman]

I think someone from @Homebrew/brew needs to do the merging here. On a related note, I think I'm comfortable enough with my newly acquired Ruby skills, and understanding of the work flows to be added to the brew team if others are comfortable/cool with it. Happy either way.