Fix broken links to js-stellar-base repo in release instructions (#647)

Author: Paul Bellamy

CONTRIBUTING.md

@@ -6,7 +6,7 @@ Then please [sign the Contributor License Agreement](https://docs.google.com/for
 
 
 # Releasing
-Just like with the [js-stellar-base](https://github.com/stellar/js-stellar) library, there are a few important things to remember when releasing a new version of the library.
+Just like with the [js-stellar-base](https://github.com/stellar/js-stellar-base) library, there are a few important things to remember when releasing a new version of the library.
 
 In fact, you should follow [the steps there](https://github.com/stellar/js-stellar-base/blob/master/CONTRIBUTING.md#Releasing), first, except for this repository. Then, **if base has been updated**, you want to follow the additional steps here: