Host with port generates invalid signature

[severien]

Hi, I have been testing this library and noticed that when using a host with port the library generates a signature without the port as host header.
Example: http://localhost:8080

Expected header in canonical request.
host:localhost:8080

Actual header used for canonical request:
host:localhost

[theherk]

Interesting. One wouldn't intuit that the host header wants both the host and the port, but it does. Good find. I'll bet they'd accept a pull request that fixes it.