added "clean" option before compiling

zeitlaeufer/compileProject.sh

@@ -1,4 +1,8 @@
 #!/usr/bin/env bash
 set -uo pipefail
 
-javac -Xlint -d target/ src/**/*.java
+if [[ $# -ge 1 && $1 == "clean" ]]; then
+   rm -r target/;
+fi
+
+javac -Xlint -d target/ src/**/*.java;