Update: Dec 8, 2014

cluster_distribution.py: updated how the Class distribution is treated
by recalculating the half-lives so these are consistent with the
Perseus distribution. This means that the user now supplies an age
rather than a Class distribution.

cluster_emission.py: significantly updated in several aspects:
1. units are now treated appropriately and everything is calculated in
Jy/pixel before being converted to Jy/bea,
2. the outflow lobes are now 2D Gaussians instead of boxes
3. the routine checks for how envelope mass and intensity are
correlated based on t statistics. If there is no linear correlation,
the routine checks for a power-law correlation before exiting if no
correlation is found

Still to do:
- Upgrade routine to write out resulting image in FITS format
- Handle 3D spectral cubes, i.e. do the velocities appropriately
- Write proper documentation