Update README.md

Some dependencies were missing - fftw, libsamplerate. I haven't added them for Mac/Windows since I don't know how. Also cleaned up the file generally a bit.
Merge pull request #14 from Timmmm/patch-1

Update README.md
Don't scrobble tracks as soon as they get cached.
Allow a proxy to be changed back to NoProxy.
Use QNetworkProxyFactory::systemProxyForQuery for proxy settings. Removes dependency on MSVC and hopefully fixes rare hang on startup bug when finding initial proxy settings.