Revert "temporarily fork atto"

This reverts commit 10e2288.

Author: SethTisue

configs/project-refs.conf

@@ -13,7 +13,7 @@ vars.uris: {
   ammonite-uri:                 "https://github.com/lihaoyi/ammonite.git"
   argonaut-uri:                 "https://github.com/argonaut-io/argonaut.git"
   async-uri:                    "https://github.com/scala/async.git"
-  atto-uri:                     "https://github.com/SethTisue/atto.git#scala-version-checking"
+  atto-uri:                     "https://github.com/tpolecat/atto.git#series/0.5.x"
   better-files-uri:             "https://github.com/pathikrit/better-files.git"
   blaze-uri:                    "https://github.com/http4s/blaze.git#v0.12.4"
   breeze-uri:                   "https://github.com/scalanlp/breeze.git"