update todo

todo.txt

 (A) check divfree function
 (B) FFTW interpolator doesn't need its own field            @optimization +v1.0
 (B) compute z polynomials only when needed                  @optimization +v1.0
-(B) see if HDF5 performance can be improved                 @optimization +I/O
+(B) read https://www.xsede.org/documents/271087/369161/ExtScale-Koziol.pdf  @optimization @HDF5 +I/O
 (B) split library into core and extra                       @optimization +v1.0
+(B) tweak HDF5 settings                                     @optimization @HDF5 +I/O
 (B) use less memory                                         @optimization
 (C) clean up machine_settings mess                          @design @documentation +v2.0
 (C) code overview                                           @documentation
+(C) compute kMeta(t) as well
 (C) move stat I/O to cpp lib                                @design @HDF5
 (C) set up mechanism for adding in new PDEs                 @design +v2.0 +alternate_algorithms
 (C) test involving hydrodynamic similarity                  @tests