[README] Add section on release configuration

.gitignore

@@ -1,3 +1,4 @@
 */
 .github_access_token
 options.yml
+topological_order.txt

README.md

@@ -70,6 +70,22 @@ $ rake -T
 - `update_rubocop_configuration[gem_dir]`: Update the shared CocoaPods RuboCop
   configuration for the given repo or for all the repos.
 
+### Release Configuration
+
+If you're using Rainforest to do releases on any of the CocoaPods gems,
+there are a few extra setup steps.
+
+- Create a `.github_access_token` in the root of this repo containing a GitHub
+  access token. This is needed to create GitHub releases via the GitHub API.
+- Create an `options.yml` file specifying the locations of `Strata`, `Bundler`,
+  and `RubyGems`. For example:
+
+  ```yaml
+  strata: ~/Development/Strata
+  bundler: ~/Development/OpenSource/bundler
+  rubygems: ~/Development/OpenSource/rubygems
+  ```
+
 
 ## Collaborate
 

Rakefile

@@ -1094,17 +1094,21 @@ namespace :ensure_master_and_clean do |ensure_master_and_clean|
   end
 
   %w(bundler rubygems).each do |repo|
-    task repo do
-      ensure_master_and_clean!(File.expand_path(options[repo]))
+    if repo_dir = options[repo]
+      task repo do
+        ensure_master_and_clean!(File.expand_path(repo_dir))
+      end
     end
   end
 
   namespace :strata do |strata|
-    strata_dir = File.expand_path(options['strata'])
-    error('Missing Strata.') unless File.directory?(strata_dir)
-    Dir[File.join(strata_dir, '*/')].each do |repo|
-      task File.basename(repo) do
-        ensure_master_and_clean!(repo)
+    if strata_dir = options['strata']
+      strata_dir = File.expand_path(strata_dir)
+      error('Missing Strata.') unless File.directory?(strata_dir)
+      Dir[File.join(strata_dir, '*/')].each do |repo|
+        task File.basename(repo) do
+          ensure_master_and_clean!(repo)
+        end
       end
     end