APT source whitelist request for ppa:masterminds/glide

Please add the PPA for [the Glide tool](https://github.com/Masterminds/glide) to the source white list.
For verification, you can see the source line specified in [Glide's public documentation](https://github.com/Masterminds/glide#install).

Source line: [`ppa:masterminds/glide`](https://launchpad.net/~masterminds/+archive/ubuntu/glide)
