Issue with Signing AWS Requests for Paths Starting with Double Slash

[OfirSWiz]

I have encountered an issue while using the library to sign AWS request, specifically when the requests start with a double slash (e.g., when an object in S3 contains a forward slash '/'). After investigating the source code, it appears that the problem lies in the amz_cano_path function, which incorrectly replaces double slashes with a single slash.

Expected Behavior:
The library should correctly handle paths starting with a double slash and generate valid signatures for AWS requests without altering the path.

Proposed Solution:
To address this issue, I suggest modifying the amz_cano_path function to correctly handle paths starting with a double slash. The function should preserve the original path without replacing double slashes with a single slash.
This could be fixed by removing the following line fixed_path = re.sub('/+', '/', fixed_path)

[tedder]

Interesting discovery. Probably right not to double it, though I wonder if that'll cause a regression. Feel free to contribute a PR (especially if there's a unit test).