remove ability to install additional packages

did't work out as expected. For starters, it doesn't allow updating of
packages in the chroot.
add postfix to mock chroot path
automatically clean up mock chroot
print which quirks were used when comparing
print the name of the srpm for non-reproducible builds

allows for easier greping
ignore gcc checksum files for now
set sourcedir to correctly parse spec files
check all rpms for differences
don't nuke root cache on startup

better do this optimization outside the script as needed
work around yum bug 1125387
always test reproducibility first

add an argument to quit afterwards