addresses #10151
creating custom 404 for old chill notice not yet available and fixing typo in 422 page.
Merge pull request #268 from apatel/custom_404

custom 404 for old chill notices
Merge pull request #267 from berkmancenter/fix_ooming

addresses #10151
making tests pass
Merge pull request #270 from apatel/custom_404

making tests pass
Merge pull request #269 from berkmancenter/custom_404

for Task #10181