added dependencies to README
added function to get the box to use to calculate sigma
added function to calculate center and fwhm of peak

NOTE: the fwhm is very dependent on the bin sizes,
and if the bins are too small, then the data is two noisy
and we get multiple zeros. I don't know what to do about this,
should we try and fit a gaussion, or a poisson distribution thing?
I just don't know what to do right now.
now calculate sigma with trimmed standard deviation
moved fwhm function to calc_params
params now sets up all paramaters needed for daophot
Merge branch 'hist_sigma' into thirdpass

Conflicts:
	README.md