Update to Zenodo citation

CITATION

@@ -1,5 +1,5 @@
 Please cite as:
 
-Library Carpentry:
-"Shell Lessons for Libraries."
-June 2016, https://librarycarpentry.github.io/lc-shell/.
+Danielle Kane (Ed.), Anna Oates (Ed.), John Wright (Ed.), Nilani Ganeshwaran (Ed.), Tim Dennis (Ed.), Belinda Weaver (Ed.), James Baker, Christopher Erdmann, Dan Michael Heggø, Katrin Leinweber, hugolio, … Vikram Chhatre. (2019, July). LibraryCarpentry/lc-shell: Library Carpentry: The UNIX Shell, June 2019 (Version v2019.06.1). Zenodo. http://doi.org/10.5281/zenodo.3266085
+
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.3266085.svg)](https://doi.org/10.5281/zenodo.3266085)