Update contributing docs (#564)

CONTRIBUTING.md

@@ -1,12 +1,17 @@
 Contributing
 ============
 
-If you would like to contribute code to analytics-ios you can do so through
+If you would like to contribute code to `analytics-ios` you can do so through
 GitHub by forking the repository and sending a pull request.
 
+Development occurs on the `dev` branch, and pull requests must be opened against
+the `dev` branch. Every second Wednesday, `master` is taggged and released, and
+`dev` is merged into `master`. In general, code will be available on `master`
+for two weeks before being tagged as a stable release.
+
+Critical bug fixes will be cherry picked into `master` after being merged into
+`dev` and released immediately.
+
 When submitting code, please make every effort to follow existing conventions
 and style in order to keep the code as readable as possible. Please also make
-sure your code compiles by running `make test` or `make xctest`.
-
-If you are interested in adding your own integration, please read the wiki for
-more [detailed documentation](https://github.com/segmentio/analytics-ios/wiki/Writing-Integrations).
+sure your code compiles by running `make build test`.