Don't submit the .gradle directory

[DavidWhitlock]

One student's GitHub repository included a .gradle directory in the phonebill-android directory. This resulted in this error during submission:

Exception in thread "main" java.util.zip.ZipException: duplicate entry: gradle/accessors/dm/LibrariesForLibs.java
	at java.base/java.util.zip.ZipOutputStream.putNextEntry(ZipOutputStream.java:259)
	at edu.pdx.cs.joy.grader.ZipFileMaker.makeZipFile(ZipFileMaker.java:43)
	at edu.pdx.cs.joy.grader.ZipFileOfFilesMaker.makeZipFile(ZipFileOfFilesMaker.java:40)
	at edu.pdx.cs.joy.grader.Submit.makeZipFileWith(Submit.java:657)
	at edu.pdx.cs.joy.grader.Submit.submit(Submit.java:327)
	at edu.pdx.cs.joy.grader.Submit.parseCommandLineAndSubmit(Submit.java:884)
	at edu.pdx.cs.joy.grader.SubmitAndroidProject.main(SubmitAndroidProject.java:52)

The submit program should not submit the .gradle directory.