Simplified base plotting class so everything can inherit from it.
	modified:   plotting.py
If no title, save figures without.
	modified:   plotting.py
remove 'current_snapshot' attribute from sim class.
	modified:   sim.py
Include simulation data in snapshot initialization.
	modified:   sim.py
	modified:   snapshot.py
Include 'centering' in kwargs.
	modified:   visualize.py
Modularized density_projection()
	modified:   visualize.py
Generalized the density projection method.
	modified:   visualize.py
find_center uses **kwargs instead of explicit list.
	modified:   analyze.py
set_viewpoint() uses kwargs. dulication of 'centering' keyword resolved.
	modified:   visualize.py
bugfix.
	modified:   analyze.py
density projection added to Image class.
	modified:   plotting.py
Added new class for sink data.
	modified:   sinks.py
Added sink data placeholders to snapshot class.
	modified:   snapshot.py
When refining, don't exclude sinks.
	modified:   hdf5.py
Sink tracking implemented.  Still need to get units right...
	modified:   analyze.py
	modified:   hdf5.py
	modified:   plotting.py
	modified:   sim.py
	modified:   sinks.py
	modified:   snapshot.py
	modified:   visualize.py
New class for gathering unit information.
	modified:   sim.py
	modified:   units.py
Fixed an assload of typos.
Note to self: don't commit without checking to see if it runs!
	modified:   units.py
Changed default behavoir to not track sinks.
	modified:   sim.py
Basic unit tracking structure in place.
	modified:   hdf5.py
	modified:   nbody.py
	modified:   snapshot.py
	modified:   sph.py
New unit tracking system completed.
	modified:   hdf5.py
	modified:   sph.py
	modified:   units.py
	modified:   visualize.py