Skip downloading resources from file:// or resource://

[groovecoder]

Steps to reproduce:

1. Include the <script> tag on a page with protocol-relative paths to CSS resources. E.g., <link href="//mozorg.cdn.mozilla.net/media/css/tabzilla-min.css" rel="stylesheet">
2. Hit the page
3. Start analysis for the domain

Expected results:
Should see analysis report for the page

Actual results:
Alligator worker shows traceback:

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/django/core/management/base.py", line 390, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/django/core/management/base.py", line 441, in execute
    output = self.handle(*args, **options)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/webalyzer/base/management/commands/run-gator.py", line 14, in handle
    worker.run_forever()
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/alligator/workers.py", line 99, in run_forever
    result = self.gator.pop()
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/alligator/gator.py", line 145, in pop
    return self.execute(task)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/alligator/gator.py", line 215, in execute
    return task.run()
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/alligator/tasks.py", line 250, in run
    result = self.func(*self.func_args, **self.func_kwargs)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/webalyzer/analyzer/views.py", line 171, in start_analysis
    processor.process_html(page.html, page.url)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/mincss/processor.py", line 215, in process_html
    self.blocks[key] = self._download(link_url)
  File "/Users/lcrouch/code/py_sandbox/webalyzer/venv/lib/python2.7/site-packages/mincss/processor.py", line 99, in _download
    raise IOError(url)
IOError: file://mozorg.cdn.mozilla.net/media/css/tabzilla-min.css

[peterbe]

This sounds like a bug in mincss.
It should pick up its scheme from the URL of the page.