Merge pull request #116 from cmu-delphi/80-could-also-mention-epi_archive-functionality-eg-data-structures-or

Mentioned `epi_archive` functionality and changed "over space and time" in package description

Author: dajmcdon

DESCRIPTION

@@ -15,9 +15,10 @@ Authors@R: c(
     person("Dmitry", "Shemetov", role = "ctb"),
     person("Ryan", "Tibshirani", , "ryantibs@cmu.edu", role = c("aut", "cre"))
   )
-Description: This package introduces a common data structure for
-    epidemiological data sets measured over space and time, and offers
-    associated utilities to perform basic signal processing tasks.
+Description: This package introduces a common data structure for epidemiological
+    data reported by location and time, provides another data structure to
+    work with revisions to these data sets over time, and offers associated
+    utilities to perform basic signal processing tasks.
 License: MIT + file LICENSE
 Imports: 
     data.table,