v0.0.50: Minor changes

acmetool now sets umask to 0 on launch, to ensure that webroot
files can be written world-readable.

Changed back to using cheggaaa/pb rather than branch, now that
changes have been merged upstream.

Responder listen addresses are now intelligently sorted.

CSRs now contain a CN, which is the first name specified in
a target, which can help ensure that that name ends up as the
CN in the final certificate.

Fixed typos.

The Ubuntu(/Debian) PPA now provides arm and arm64 builds.
These should work on ARM platforms with and without hardfloat support.