update todo

done.txt

@@ -9,3 +9,4 @@ x 2016-01-03 compute kMeta(t) as well
 x 2016-01-03 split library into core and extra                                       @optimization +v1.0
 x 2016-01-07 FFTW interpolator doesn't need its own field                            @optimization +v1.0 +particle_api
 x 2016-01-08 simplify tracer/field addition mechanism                                @design +v1.0 +particle_api
+x 2016-01-08 add stat choice parameter to add_particles                              @design +v1.0 +particle_api

todo.txt

-(B) add stat choice parameter to add_particles                              @design +v1.0 +particle_api
 (B) compute z polynomials only when needed                                  @optimization +v1.0
 (B) read https://www.xsede.org/documents/271087/369161/ExtScale-Koziol.pdf  @optimization @HDF5 +I/O
 (B) set up mechanism for adding in new PDEs                                 @design +v2.0 +alternate_algorithms