Bump rust-phf version

sfackler · sfackler · commit 731ab310ba0c · 2014-03-12T00:23:52.000-07:00
diff --git a/submodules/rust-phf b/submodules/rust-phf
@@ -1 +1 @@
-Subproject commit 9b21652238c3110feccd9edc68eb0dd1d5d47aa0
+Subproject commit ba1a08d0c78a3aa672be46ab54eb00db7d6b81a9
