How can I stream all audio from my Mac to my Android phone?

Rogue Amoeba's Airfoil will do what you want. Run Airfoil on your Mac and the Airfoil Speakers app on your Android device.

Alternatively, there may be free solutions. The protocol used by Apple devices to send audio to e.g. AppleTV and Airport Express devices is called Airplay and has been reverse-engineered by projects such as Shairport. There may be an Android app which emulates this protocol to make your phone into an Airplay destination. However you'll have to search carefully as the more common implementation is to enable the Android device to send audio to the AppleTV etc.

I share my music from Mac with ArkMS http://arkmc.com/mac-osx-media-streaming-server-upnp-dlna/! Simply select folders with mp3 files and listen them on iPhone/Android in 8Player or ArkMS apps or Sonos speaker. It doesn't provide sound mirroring, music streaming only. Hope that helps.