Up version and add news.

DESCRIPTION

 Package: dataRetrieval
 Type: Package
 Title: Retrieval Functions for USGS and EPA Hydrologic and Water Quality Data
-Version: 2.5.6
-Date: 2016-04-18
+Version: 2.5.7
+Date: 2016-05-23
 Authors@R: c( person("Robert", "Hirsch", role = c("aut"),
     email = "rhirsch@usgs.gov"),
     person("Laura", "DeCicco", role = c("aut","cre"),

NEWS

+dataRetrieval 2.5.7
+==========
+* HEAD requests can be returned in readWQP* functions. This can give some indication on amount of data available.
+
 dataRetrieval 2.5.0
 ==========
 * Package httr is now used for web service retrievals