started modifying CHANGELOG
+# v 0.4 API changes:
+
+Summary: added halo model matter power spectrum calculation and halo mass-concentration relations. Change to sigma(R) function so that it now has time depdence: it is now sigma(R,a). Added a sigmaV(R,a) function, where sigmaV(R,a) is the variance in the displacement field smoothed on scale R at scale-factor a.
+
+## C library
+In ccl_halomod.c:
+
+## Python library
+
# v 0.3 API changes:
Summary: the user interface for setting up cosmologies with neutrinos has been altered. Users should from now on pass Neff, the effective number of relativistic neutrino species in the early universe, and mnu, either a sum or neutrino masses or a set of 3 neutrinos masses.
