Merge pull request #105 from cmu-delphi/replace_proxy_references

update base url to `api.delphi.cmu.edu`

Author: dshemetov

R/constants.R

@@ -1,3 +1,3 @@
 version <- "1.0.0"
 http_headers <- httr::add_headers("User-Agent" = paste0("epidatr/", version), "Accept-Encoding" = "gzip")
-global_base_url <- "https://api.covidcast.cmu.edu/epidata/"
+global_base_url <- "https://api.delphi.cmu.edu/epidata/"