stylistic revisions of .md files

CONTRIBUTING.md

 Peter Maneykowski (ISE undergraduate) did some early versions of the algorithm.
-Nitin Srivastava (M.S. in ISE) wrote a thesis connected to this work.
+Nitin Srivastava (M.S. in ISE) wrote a thesis connected to this work.
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+
+Thanks to Maureen McGuire of Crisalida Farms.
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README.md

-This is the code for 
-Algorithmic Geolocation of Harvest in Hand-Picked Agriculture
-by Srivastava, Maneykowski, and Sowers
+Srivastava N, Maneykowski P, Sowers RB. Algorithmic geolocation of harvest in hand-picked agriculture. Natural Resource Modeling. 2018;31:e12158. <https://doi.org/10.1111/nrm.12158>
+
+By
+Richard Sowers <r-sowers@illinois.edu>, website
+<http://publish.illinois.edu/r-sowers/>
 
-Richard Sowers r-sowers@illinois.edu
 
-Main file is