Update contributing doc (#1097)

Provide more info to Sceptre contributors

CONTRIBUTING.md

@@ -8,14 +8,15 @@ the project.
 This project adheres to the Contributor Covenant
 [code of conduct](http://contributor-covenant.org/version/1/4/). By
 participating, you are expected to uphold this code. Please report unacceptable
-behaviour to sceptre@cloudreach.com.
+behaviour to the [Sceptre github discussion](https://github.com/Sceptre/sceptre/discussions).
 
 # How to Contribute
 
 ## Report Bugs
 
 Before submitting a bug, please check our
-[issues page](https://github.com/cloudreach/sceptre/issues) to see if it's
+[issues page](https://github.com/cloudreach/sceptre/issues) and
+[discussion board](https://github.com/Sceptre/sceptre/discussions) to see if it's
 already been reported.
 
 When reporting a bug, fill out the required template, and please include as much
@@ -89,32 +90,51 @@ $ git clone git@github.org:<github_username>/sceptre.git
 $ git checkout -b <branch-name>
 ```
 
-5. When you're done making changes, check that your changes pass linting, unit
-   tests and have sufficient coverage and integration tests pass:
+5. When you're done making changes, check that your changes pass
+   [linting](#Linting), [unit tests](#Unit-Tests) and have
+   sufficient coverage and [integration tests](#Integration-Tests)
+   pass.
 
-   Check linting:
+6. Make sure the changes comply with the pull request guidelines in the section
+   on `Contributing Code`.
+
+7. Commit and push your changes.
+
+   Commit messages should follow
+   [these guidelines](https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
+
+   Use the following commit message format
+   `[Resolves #issue_number] Short description of change`.
+
+   e.g. `[Resolves #123] Fix description of resolver syntax in documentation`
+
+8. Submit a pull request through the GitHub website.
+
+## Linting
 
 As a pre-deployment step we syntatically validate files with
 [pre-commit](https://pre-commit.com).
 
 Please [install pre-commit](https://pre-commit.com/#install) then run
 `pre-commit install` to setup the git hooks.  Once configured the pre-commit
 linters will automatically run on every git commit.  Alternatively you
-can manually execute the validations by running
-`pre-commit run --all-files`.
+can manually execute the validations by running `pre-commit run --all-files`.
+
+## Unit Tests
 
 Run unit tests or coverage in your current environment - (handy for quickly
 running unit tests):
 
 ```bash
-$ make test $ make coverage
+$ make test
+$ make coverage
 ```
 
-Note: Sceptre aims to be compatible with Python 2 & 3, please run unit test
+Note: Sceptre aims to be compatible with Python 3, please run unit test
 against both versions. You will need the corresponding versions of Python
 installed on your system.
 
-Run unit tests and coverage using tox for Python 3.6 and 3.7:
+Run unit tests and coverage using tox for multiple Python versions:
 
 ```bash
 $ tox -e py36 -e py37
@@ -123,7 +143,7 @@ $ tox -e py36 -e py37
 If you use pyenv to manage Python versions, try `pip install tox-pyenv` to make
 tox and pyenv play nicely.
 
-Run integration tests:
+## Integration Tests
 
 If you haven't setup your local environment or personal CircleCI account to run
 integration tests then follow these steps:
@@ -145,50 +165,43 @@ your tests are passing):
 - Add your `Access Key ID` and `Secret Access Key` that is associated with an
   IAM User from your AWS account. The IAM User will require "Full" permissions
   for `CloudFormation` and `S3` and Write permissions for `STS` (AssumeRole).
+  For an example please take a look at the Sceptre
+  [CI service user policy](https://github.com/Sceptre/sceptre-aws/blob/master/config/prod/sceptre-integration-test-service-access.yaml#L5-L35)
 
 Once you have set up CircleCi any time you commit to a branch in your fork all
 tests will be run, including integration tests.
 
 You can also (optionally) run the integration tests locally, which is quicker
 during development.
 
-To run integration tests locally:
+### To run integration tests locally
+
 * `pip install awscli`
 * Setup [AWS CLI Environment variables](https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-envvars.html)
   to work with an AWS account that you have access to.  You can use the same user
   that you use for CircleCi.
 * `pip install behave`
 
-run:
+_Note_: All integration tests are setup to run in `eu-west-*` region.  If you prefer
+to run in a different region you must update the region in each test before running it
+
+### run all tests
 
 ```bash
 $ behave integration-tests
 ```
 
-or to run a specific tests:
+### run a specific feature
 
 ```bash
-$ behave integration-tests -n "scenario-name"
+$ behave integration-tests --include <feature-file>
 ```
 
-_Note_: All integration tests are setup to run in `eu-west-*` region.  If you prefer
-to run in a different region you must update the region in each test before running it.
-
-
-6. Make sure the changes comply with the pull request guidelines in the section
-   on `Contributing Code`.
-
-7. Commit and push your changes.
-
-   Commit messages should follow
-   [these guidelines](https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
+### run a specific scenario
 
-   Use the following commit message format
-   `[Resolves #issue_number] Short description of change`.
-
-   e.g. `[Resolves #123] Fix description of resolver syntax in documentation`
-
-8. Submit a pull request through the GitHub website.
+```bash
+$ behave integration-tests -n "<scenario-name>"
+```
 
 # Credits