added adm-zip package to allow synchronous zipping of files from problems
added adm-zip package to allow synchronous zipping of files from problems

parasgithub/PrairieLearn,tbretl/PrairieLearn,kevinwang/PrairieLearn,PrairieLearn/PrairieLearnHack,lotrfan/PrairieLearn,mwest1066/PrairieLearn,kevinwang/PrairieLearn,kevinwang/PrairieLearn,kevinwang/PrairieLearn,parasgithub/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,rbessick5/PrairieLearn,mwest1066/PrairieLearn,rbessick5/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,lotrfan/PrairieLearn,kevinwang/PrairieLearn,PrairieLearn/PrairieLearnHack,mwest1066/PrairieLearn,jakebailey/PrairieLearn,kevinwang/PrairieLearn,tbretl/PrairieLearn,parasgithub/PrairieLearn,jakebailey/PrairieLearn,lotrfan/PrairieLearn,PrairieLearn/PrairieLearnHack,jakebailey/PrairieLearn,PrairieLearn/PrairieLearnHack,lotrfan/PrairieLearn,rbessick5/PrairieLearn,rbessick5/PrairieLearn,PrairieLearn/PrairieLearnHack,kevinwang/PrairieLearn,lotrfan/PrairieLearn,rbessick5/PrairieLearn,lotrfan/PrairieLearn,PrairieLearn/PrairieLearnHack,lotrfan/PrairieLearn,tbretl/PrairieLearn,jakebailey/PrairieLearn,PrairieLearn/PrairieLearnHack,mwest1066/PrairieLearn,PrairieLearn/PrairieLearnHack,mwest1066/PrairieLearn