Multiple changes from v2 including: Modifications to power_spectrum routines to read in CAMB output spectra without modifications (i.e. converting to dimensionless log pk); Reshuffling of main routine to make it easier to understand; Ability to read in a list of output redshifts and timesteps; GADGET-style outputting; The beginnings of LIGHTCONE functionality. NOTE: The lIGHTCONE and GADGET_STYLE parts are untested.