Update: A ‘c’ snapshot has been released and will be downloaded automatically by the launcher
To get the snapshot, use the new launcher available in the link below. To return to 1.5.2, simply start the old launcher and play as normal.
Cross-platform jar: https://minecraftlucky.com/dowload/file-961
Windows EXE: https://minecraftlucky.com/dowload/file-962