fixed issue #3: a simple file check on the key is now performed before creating the tomb

src/tomb

@@ -316,6 +316,12 @@ create_tomb() {
 	    return 1
     fi
     
+    if [ -e ${tombdir}/${tombfile}.key ]; then
+        error "tomb key already exists. Quitting."
+        ls -lh ${tombdir}/${tombfile}.key
+        return 1
+    fi
+
     notice "Creating a new tomb in ${tombdir}/${tombfile}"
 
     if [ -z $SIZE ]; then