Add urls to DESCRIPTION paragraph

Author: dwinter

DESCRIPTION

@@ -23,9 +23,10 @@ Suggests:
     rmarkdown
 URL: http://github.com/ropensci/rentrez
 BugReports: https://github.com/ropensci/rentrez/issues
-Description: Provides an R interface to the NCBI's EUtils API
-    allowing users to search databases like GenBank and PubMed, process the
-    results of those searches and pull data into their R sessions.
+Description: Provides an R interface to the NCBI's 'EUtils' API, allowing users 
+to search databases like GenBank <https://www.ncbi.nlm.nih.gov/genbank/>and 
+PubMed <https://www.ncbi.nlm.nih.gov/pubmed/>, process the results of those 
+searches and pull data into their R sessions.
 VignetteBuilder: knitr
 Roxygen: list(wrap = FALSE)
 License: MIT + file LICENSE