Update CHANGES file for 5.2.

Also add more detailed documentation of new timesteppers.
Merge pull request #425 from ketch/update_changes

Update CHANGES file for 5.2.
PyWENO: Update weno.py to match current PyWENO release.
Merge pull request #429 from memmett/memmett-pyweno

PyWENO: Update weno.py to match current PyWENO release.
ability to take tfluct solver as input in solver
euler 1d example modified to use new solver tfluct workflow
added dimension dependenpt tfluct stub functions