Merge pull request #49 from nanxstats/citation-key

Add `key` to `inst/CITATION`

Author: nanxstats

inst/CITATION

@@ -1,11 +1,12 @@
 bibentry(
   "Article",
+  key = "xiao2015protr",
   title = "protr/{ProtrWeb}: {R} package and web server for generating various numerical representation schemes of protein sequences",
   author = "Nan Xiao and Dong-Sheng Cao and Min-Feng Zhu and Qing-Song Xu",
-  year = 2015,
   journal = "Bioinformatics",
   volume = 31,
   number = 11,
   pages = "1857--1859",
-  doi = "10.1093/bioinformatics/btv042",
+  year = 2015,
+  doi = "10.1093/bioinformatics/btv042"
 )