uncorrected proofs should be in subdirectory of corpus dir

[eseiver]

if allofplos is pip installed, updating it will erase the uncorrected proofs list and potentially the corpus itself. one thing to help with this is make the uncorrected proofs list into a . system file in the corpus directory that is explicitly ignored otherwise.
edit: won't solve this problem, but a subdirectory instead of a list would eliminate the need for said list.