Fix argument parsing to accept delay as a number

Hi,
I found that when I specified a delay (such as --delay 5) when running dumpgenerator.py, I received the error:
```
Traceback (most recent call last):
  File "dumpgenerator.py", line 1562, in <module>
    main()
  File "dumpgenerator.py", line 1554, in main
    createNewDump(config=config, other=other)
  File "dumpgenerator.py", line 1258, in createNewDump
    titles += getPageTitles(config=config, session=other['session'])
  File "dumpgenerator.py", line 325, in getPageTitles
    titles = getPageTitlesAPI(config=config, session=session)
  File "dumpgenerator.py", line 201, in getPageTitlesAPI
    config=config, session=session)
  File "dumpgenerator.py", line 170, in getNamespacesAPI
    delay(config=config, session=session)
  File "dumpgenerator.py", line 61, in delay
    print 'Sleeping... %d seconds...' % (config['delay'])
TypeError: %d format: a number is required, not str
```
Specifying a type (float) when using argparse will allow the delay argument to be read as a number, not a string. Please let me know if this fix is acceptable, thanks!