Updates to the Contributing.md file.

Summary:
Issue fixed: #473

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/558

Differential Revision: D4797501

Pulled By: jessesquires

fbshipit-source-id: e197283f30781017e6fd76a6c604599a4f480e69

.github/CONTRIBUTING.md

@@ -28,6 +28,18 @@ IGListExperimentEnabled(self.experiments, IGListExperimentMyAwesomeChange) {
 
 Once your experiment is confirmed we will remove the option and wrapping check!
 
+## How we do major and minor releases
+
+Everything merges into master. When we cut a release, we merge from `master` into `stable`, tag, and push to CocoaPods.
+
+*Example:*
+
+If current release is `2.1.0`, then any commits for `2.2.0` go into `stable` while commits for `3.0` would go to `master`.
+
+## Testing
+
+Keep in mind that we want 99% test coverage at all times. If you add new code, please make sure it gets tested! When fixing bugs, try to reproduce the bug in a unit test and then fix the test. This makes sure we never regress that issue again.
+
 ## Contributor License Agreement ("CLA")
 
 In order to accept your pull request, we need you to submit a CLA. You only need
@@ -48,7 +60,10 @@ outlined on that page and do not file a public issue.
 
 * 4 spaces for indentation rather than tabs
 * Public classes and methods must contain header documentation
-* Use plain C functions whenever possible (as opposed to class methods)
+* Use plain C functions instead of class methods whenever possible
+* Restrict subclassing (`IGLK_SUBCLASSING_RESTRICTED` macro or `final` in Swift), unless the class is designed for subclassing.
+* Use instance variables instead of properties
+* Create local variables instead of repeatedly accessing properties like `self.property`. This results in a larger binary and extra `objc_msgSend(...)` calls.
 
 ## Updating Testing Dependencies
 

CHANGELOG.md

@@ -111,6 +111,8 @@ This release closes the [2.1.0 milestone](https://github.com/Instagram/IGListKit
 
 - `-[IGListAdapter updater]` is now public (read-only). [Adlai-Holler](https://github.com/Adlai-Holler) [(#379)](https://github.com/Instagram/IGListKit/pull/379)
 
+
+
 ### Fixes
 
 - Avoid `UICollectionView` crashes when queueing a reload and insert/delete on the same item as well as reloading an item in a section that is animating. [Ryan Nystrom](https://github.com/rnystrom) [(#325)](https://github.com/Instagram/IGListKit/pull/325)
@@ -242,5 +244,3 @@ You can find a [migration guide here](https://instagram.github.io/IGListKit/migr
 -----
 
 Initial release. :tada:
-
-