Add goodness of fit summary tables

[mpdougherty]

Add the functions required to produce the Goodness of Fit (GOF) tables.

[mpdougherty]

It seems like graphs would be a better visualization (y-axis: GOF stat, x-axis: river mile). This would help to quickly screen for river reaches with high error.

[mpdougherty]

If I remember correctly, I left off while I was in the process of porting code from the old phase 1 reports (https://github.com/mpdougherty/razviz/blob/master/inst/old_reports/original_Hydrographs.Rmd) to razviz functions. I got as far as creating the gof_table.R and gof_stats.R functions, but the tests for these two functions are still in progress. I created the vignette, but it is still incomplete as well.