#520 sed bug fix / chromatic aesthetics tweak

A couple of quick bug fixes to sed.py, and a couple aesthetic tweaks to chromatic.py.

1. In sed.py, add a guard for round off error effecting whether LookupTable will succeed or not.  This is already implemented in bandpass.py, and should be included here as well.
2. Also in sed.py, fix bug where the .wave_list attribute does not get adjusted when .atRedshift() method is called.
3. In chromatic.py, simplify `if len(bandpass.wave_list) > 0 or len(self.wave_list) > 0)` to just use `if len(wave_list) > 0`.  `wave_list` was created above as the union of `bandpass.wave_list` and `self.wave_list`.
4. In chromatic.py, transfer logic
```
if isinstance(self, ChromaticSum):  #Don't wrap `ChromaticSum`s, easier to just
    for obj in self.objlist:        #wrap their arguments.
        obj._applyMatrix(J)
```
from `apply*` methods to `_applyMatrix` method.