Major freezing or full lockup while zipping includes output zip file

An issue would occur when you would include the same file your are outputting as zip.
An example of this occurring is running
```shell
$ marmoset submit course assn *
```
It would pick up the assn.zip, if already submitted once before, and cause a lock up through some recursive CRC check or zipping tomfoolery going on and take a significantly longer time.

This fix just ensures that zip file isn't included as you (hopefully) wouldn't need it in submissions anyways.