salt sls files with python shebangs are not properly recognized #61

Some salt sls files are written in python directly, I've added those interpreters in a PR here #60 as well as disabled the executable checks since these files are not required to be and also disabled the optimization for skipping peeking at the file contents if we recognize the extension.. I do see how this a nice speedup though.. maybe the extensions.EXTENSIONS dict should be changed from:

EXTENSIONS = {
...
    'sh': {'text', 'shell'},
    'sls': {'text', 'salt'},
    'so': {'binary'},
...
}

to something like:

EXTENSIONS = {
...
    'sh': {
        'tags': {'text', 'shell'},
        },
    'sls': {
        'tags': {'text', 'salt'},
        'always-peek': True,
    },
    'so': {
        'tags': {'binary'},
    },
...
}

By changing each value to its own dict which could have an optional key always-peek(?) so then you could .get('always-peek', False) to check if the file should be inspected?