Allow for sorting the requirements when exporting requirements.txt

[thejcannon]

This allows for much easier diffing (migrating from pip-tools) and grokking (trying to scroll and find)

[thejcannon]

Currently I have the following:

sed -i -z "s/\\\\\n  //g" requirements.txt
sort -o requirements.txt requirements.txt
sed -i "s/ --hash=\(.*\)/ \\\\\\n  --hash=\1/" requirements.txt

[jsirois]

This seems fine, if ~arbitrary. That said, its hard to imagine too many more axes beyond alpha-sort and pip-tools is a thing.