Add outline code for spectra chi-square

[djperrefort]

This pull request adds the spectra_chisq module to the analysis pipeline. The module is functional and provides an outline on how to calculate chi-squares for the modeled spectra, but is incomplete for the following reasons:

1. Error-values are not available for the DR1 spectra. For now, I'm using a tenth of the flux values just to have numerical values that can be used to ensure the code runs.
2. No color warping is applied to the spectra, but there is a placeholder function

Relevent issue: #10