Update contribution guide
Update contribution guide

librsync/librsync,yrgoldteeth/librsync,dbaarda/librsync,sourcefrog/librsync,dbaarda/librsync,librsync/librsync,sourcefrog/librsync,librsync/librsync,dbaarda/librsync,yrgoldteeth/librsync,yrgoldteeth/librsync,sourcefrog/librsync,librsync/librsync,dbaarda/librsync,yrgoldteeth/librsync,sourcefrog/librsync