finished section 3 and 4 of the vignette.
updated .pdf of vignette
Merge pull request #1 from USGS-R/master

Finished sections 2 and 3 of vignette
fixed the spelling of fluorescence throughout the vignette.
added references to vignette
Merge branch 'master' of github.com:schristel-USGS/USGSHydroOpt
Added to the introduction
added a conclusion section
more changes to vignette
Merge pull request #10 from schristel-USGS/master

update changes to vignette