Implement operator traits on references

Fixes #81.

Author: mbrubeck

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ordered-float"
-version = "2.2.0"
+version = "2.3.0"
 authors = ["Jonathan Reem <[email protected]>", "Matt Brubeck <[email protected]>"]
 license = "MIT"
 description = "Wrappers for total ordering on floats"