Fix argument for enabling GDB in template.py (#292)

The `DEBUG` argument is reserved by pwntools for turning on its
debugging output and pwntools does not expose reserved arguments in
`args`. This commit changes the argument name to `GDB` so that it does
not conflict with a reserved argument.

README.md

@@ -105,7 +105,7 @@ context.binary = exe
 def conn():
     if args.LOCAL:
         r = process([exe.path])
-        if args.DEBUG:
+        if args.GDB:
             gdb.attach(r)
     else:
         r = remote("addr", 1337)

src/template.py

@@ -10,7 +10,7 @@
 def conn():
     if args.LOCAL:
         r = process({proc_args})
-        if args.DEBUG:
+        if args.GDB:
             gdb.attach(r)
     else:
         r = remote("addr", 1337)