add wwdc16 theme

[johnpryan]

Adds a theme based on the WWDC 2016 website:

Here's a quick link to the source file for review.

Here's the plaintext palette I used, which is based on vim-wwdc16 by @lifepillar:

#25272f
#dc3c3c
#64878f
#d28e5d
#4670d8
#b73999
#00aba5
#999999
#333333
#666666
#52bd58
#95c76f
#8485ce
#ffffff

Side note: I noticed that running the generator is updating the copyrights to 2016, so I'm not 100% sure if I added all of the necessary files (I ran a quick find . -name wwdc* -print0 | xargs -0 git add to add the necessary files)

@daylerees