pip-compile should have an --exclude option for blacklisting packages from output

[ssbarnea]

There are are use cases where users may want to exclude (blacklist) a wider range of packages from being added to the output file, not only setuptools.

I am aware of at least one big project that is building constraint files with all dependencies while excluding a special list of packages from being included in the output.

I would like to propose adding an -e, --exclude filename option which would ensure that the package names from that file are not included in the output.

Does this makes sense or not?

[cjerdonek]

Is this a duplicate of #333?