Added support for downloading files with spaces in its name.

Hi,

I was doing a CLI based on your library and I found a bug in the library.

As you can see, if the filename of the download contains spaces, the message.split will not divide the params as expected, so the download fails.

I have implemented a regexp parser that deals with those filenames. You can see the regexp in action, with some test cases here: https://www.debuggex.com/r/Af2T3HrboNA0-I6L.

If you are interested, I can also do a pull request with the CLI (it's on my fork, if you want to take a look).

Cheers,

Octavi