TryFrom stable

TryFrom is now stable, so use that. Additionally re-export OrderedFloat since
it is used by the generated code. Relax dependencies to reduce downstream
conflicts.
diff --git a/lib/rs/Cargo.toml b/lib/rs/Cargo.toml
index 3a25b16..bad2a38 100644
--- a/lib/rs/Cargo.toml
+++ b/lib/rs/Cargo.toml
@@ -11,9 +11,8 @@
 keywords = ["thrift"]
 
 [dependencies]
-byteorder = "~1.2.1"
-integer-encoding = "~1.0.4"
-log = "~0.3.8"
-threadpool = "~1.7.1"
-try_from = "~0.2.2"
-
+ordered-float = "0.5"
+byteorder = "1"
+integer-encoding = "1"
+log = "0.4"
+threadpool = "1.7"