update homebrew formula docs

Formula/README.md

@@ -1,18 +1,41 @@
 # Maintaining Homebrew Formula
 
-In order to update to a new release:
+## Update Formula
+
+This should be done each time a release is cut. See: [RELEASES](../RELEASES.md)
 
 1. go to https://github.com/appnexus/ankh/releases to get the URL for the **source** tarball
 
-2. `brew create <release tarball url>` - note the line of the output "For your reference the SHA-256 is: <sha-256>"
+2. get sha256
+
+```sh
+$ curl -s <source tarball url> | shasum -a 256 -
+<sha-256 result> -
+```
+
+*example:*
+
+```sh
+$ curl -s https://github.com/appnexus/ankh/archive/v2.1.0.tar.gz | shasum -a 256 -
+770e8e5bacb91b93985ea05f2fcd3ea30faf8ad0a4fda32b61164cd051c29042  -
+```
 
 3. update Formula/ankh.rb with:
 
 ```
-url "`<release tarball url>`"
-sha256 "`<sha-256>`"
+url "`<source tarball url>`"
+sha256 "`<sha-256 result>`"
 ```
 
+*example:*
+
+```
+url "https://github.com/appnexus/ankh/archive/v2.1.0.tar.gz"
+sha256 "770e8e5bacb91b93985ea05f2fcd3ea30faf8ad0a4fda32b61164cd051c29042"
+```
+
+## Troubleshooting
+
 If you get an error like:
 
 ```