Merge pull request #91 from ldecicco-USGS/master

Updated to bibentry.

inst/CITATION

 citHeader("To cite dataRetrieval in publications, please use:")
 
-citEntry(entry = "book",
+bibentry(bibtype = "InBook",
  author = personList(
               as.person("Robert M. Hirsch"),
               as.person("Laura A. De Cicco")),
   title = "User guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R packages for hydrologic data",
-  publisher = "U.S. Geological Survey Techniques and Methods",
-  year = "2015",
+  booktitle = "Techniques and Methods",
+  institution = "U.S. Geological Survey",
+  year = 2015,
+  chapter = "A10",
   url = "http://pubs.usgs.gov/tm/04/a10/",
   textVersion = "Hirsch, R.M., and De Cicco, L.A., 2015, User guide to Exploration and Graphics for RivEr Trends (EGRET) and dataRetrieval: R packages for hydrologic data (version 2.0, February 2015): U.S. Geological Survey Techniques and Methods book 4, chap. A10, 93 p., http://dx.doi.org/10.3133/tm4A10"
 )