Add DEVELOPMENT.md doc (#78)

* Add DEVELOPMENT.md doc

Signed-off-by: Jiaxin Shan <[email protected]>

* Address code review feedbacks

DEVELOPMENT.md

@@ -0,0 +1,67 @@
+## Development Guidelines
+
+This doc is a development guidance for Kubeflow/common developers.
+
+## Git development cycle
+
+We use [git flow](https://guides.github.com/introduction/flow/) workflow and please check it out to get familiar with the process. 
+
+## Before PR submission 
+
+Before submitting a pull request, make sure the code passes all the tests and is clean of lint errors:
+
+### Build
+
+```bash
+# cd into the root directory
+go build ./...
+```
+
+### Format
+
+```bash
+# format your code
+go fmt ./...
+```
+
+### Code generation
+
+```bash
+# make sure you generate code if you make api level changes
+./hack/update-codegen.sh
+```
+
+```bash
+# check your api and client are update to date.
+./hack/verify-codegen.sh
+```
+
+### Code from upstream Kubernetes
+
+Following folder includes some auxiliary codes to help us easily build operator. 
+Codes are from Kubernetes internal package [controller_utils.go](https://github.com/kubernetes/kubernetes/blob/master/pkg/controller/controller_utils.go),
+This help us remove directly dependency on Kubernetes. If we want to see more details, please check issue [#48](https://github.com/kubeflow/common/issues/48).
+
+- [control](./pkg/controller.v1/control)
+- [expectation](./pkg/controller.v1/expectation) 
+
+Note: Please don't edit these files. If you have any issues on them, feel free to file an issue.
+
+We have a long term plan to move codes to [kubernetes/client-go](https://github.com/kubernetes/client-go). 
+See issue [kubernetes/client-go/issues/332](https://github.com/kubernetes/client-go/issues/332) for more details.
+
+
+## For repository owners
+
+For the repository owners and maintainers, please check following guidance.
+
+### Commit style guide
+
+1. Always use bot to merge PRs, never manually merge PRs please.
+
+2. Release notes are generated from commits. A typical commit may looks something like:
+
+```
+Enhance maintainability of operator common module (#55, @Jeffwan)
+Add proposal for Prometheus metrics coverage (#77, @terrytangyuan)
+```