Fix typo error

[prasanthbazz]

I ran this example code and I got this exception : called read on non-open pipe.
I also tried alternate approach of SpawnInstance(). Still I get the same error.

import osquery
if __name__ == "__main__":
    instance = osquery.ExtensionClient('\\.pipe\osquery.em')
    print(instance.open())  # This may raise an exception
    client = instance.extension_client()
    client.query('select timestamp from time')

[prasanthbazz]

I figured out that it was due to wrong pipe name. It should be \.\pipe\osquery.em instead

[prasanthbazz]

The comment in the code in readme.md is misleading (https://github.com/osquery/osquery-python/blob/master/README.md#connect-to-an-existing-socket)

For windows, the pipe name should be \\.\pipe\osquery.em instead

[prasanthbazz]

#73 (comment)