Remove network request for pngquant src

[kevcenteno]

Problem

CI servers can sometimes fail to fetch the required bins and/or pngquant src.

Solution

1. Put the pngquant src in the vendor directory
2. Use binBuild.file instead of binBuild.src

[kevcenteno]

@sindresorhus Any thoughts?

[kevcenteno]

@sindresorhus Is this still maintained?

[sindresorhus]

You committed a change to vendor/linux/x64/pngquant. That needs to be removed.

[sindresorhus]

I think this is a good idea 👍

[sindresorhus]

You also need to add it to the files field in package.json

[kevcenteno]

@sindresorhus I've made the requested changes. Thank you for reviewing!

[chasebolt]

+1 on this as it would resolve a network issue i am having with this package. PR #83 can be closed out if this PR is merged in. this would also resolve #78.

[realityking]

Maybe just add vendor/src-pngquant? One less place to change when updating to a newer version.