docs: bump README to 0.0.3

Author: hellerve

README.md

@@ -7,7 +7,7 @@ Context managers for Carp. An experiment.
 You can include `using` in your project like this:
 
 ```clojure
-(load "git@github.com:carpentry-org/using@0.0.2")
+(load "git@github.com:carpentry-org/using@0.0.3")
 ```
 
 ## Usage