Notably, this also installs pip via the recommended `get-pip` route rather than
grabbing a whole new version over Homebrew; this allows the install to work with
OS X's built-in Python or with the python.org Python.
Otherwise, we sometimes end up using the system Python, for which we'd need to use sudo to install virtualenv. Brew complicates this by yelling at you if you do use sudo. So let's simplify things by always using the homebrew python, which is more up to date anyway.
This fixes an "OSError: [Errno 2] No such file or directory" on Fedora 23. Note that openssl-devel was not sufficient to install the openssl commandline tool.
The current manual-testing build of le-auto now crashes with #1548, but that should have been resolved when we upgraded the cryptography lib and so should go away when we build a new version.
Originally, I had it in mind to move letsencrypt-auto inside this dir. However, now we'd like to copy it or link it to the root level, where people are used to finding it (at least for awhile). Since it would be confusing to have a letsencrypt-auto and a letsencrypt_auto right next to each other, we rename this folder.
Peter Eckersley