Use tuples inside of `str.startswith` (for multiple checks)

[delirious-lettuce]

I checked the .travis.yml file and it says the earliest Python version being checked is 2.6. I double-checked the docs and it looks like str.startswith has accepted tuples since 2.5.

Changed in version 2.5: Accept tuples as prefix.

>>> url = 's://'
>>> url.startswith('s://') or url.startswith('://')
True
>>> url.startswith(('s://', '://'))
True

>>> url = '://'
>>> url.startswith('s://') or url.startswith('://')
True
>>> url.startswith(('s://', '://'))
True

>>> url = 'www'
>>> not url.startswith('http://') and not url.startswith('https://')
True
>>> not url.startswith(('http://', 'https://'))
True

[eliangcs]

Looks good, thanks!