start plotting
trying different finite differences in tests
somewhat working plotting function.
WIP on a bunch of random stuff, need to merge back
Merge Clare's and Kyles changes to fitting & main.

Conflicts:
	ddtpy/fitting.py
	ddtpy/main.py
cleanup in progress
cleanup finished, except tests
import some functions into top-level namespace, fix up the docs
update rtd-pip-requirements to get RTD build working
add fitsio to rtd-pip-requirements
add I/O to docs
bugfixes, update test
get rid of warnings
More steps in main.py