Correct File paths for Windows in README

[alichampi]

Hello, thank you for making this very useful project!

This is only a correction for the documentation, as Windows URIs are wrong in the README. I was using this module in Windows and it took me a while to realise why it wasn't working. Paths in Windows use \ instead of /, and Firebird respects that on the connection strings. The character is written as \\ in the code due to being a special character.

Note: This has been my experience using it with localhost and server, I haven't tried it with embedded, in theory it should be the same.