Remove TODO from master

TODO.rst

-* Check the age of the Universe at observation redshift.
-* Deal with observation without values in some filters.
-* Code Calzetti attenuation module.
-* Code ISM effect module.
-* Code AGN module.
-* Make the ISM effect a module separated from the main SED creation modules
-  and applied according to the redshift of the observation.
-* Make the ISM module work with a list (or range) of redshift to allow the
-  use of pcigale to compute photometric redshifts.
-* Code the theoretical SED serialisation and the database to store them.
-* Write documentation.