[Fixes #695] Remove install of brew ca-cert-bundle

Removed instructions to install brew ca-cert-bundle on:

- AWS instructions
- DigitalOcean instructions
- RackSpace instructions

In accordance to brew's decisions to remove the ca-cert-bundle: https://github.com/Homebrew/homebrew/commit/ab926db10c47352b38e114d0945ac1c0596eef74