Update Contributing documents

- Add `brew uninstall foo`
- Add `--build-from-source` to `brew install foo`
- Add `--new-formula` to `brew audit foo`

Closes Homebrew#3872.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,6 @@
-- [ ] Have you followed the guidelines in our [Contributing](https://github.com/Homebrew/homebrew-core/blob/master/CONTRIBUTING.md) document?
-- [ ] Have you checked to ensure there aren't other open [Pull Requests](https://github.com/Homebrew/homebrew-core/pulls) for the same formula update/change?
-- [ ] Have you built your formula locally prior to submission with `brew install <formula>` (where `<formula>` is the name of the formula you're submitting)?
-- [ ] Does your submission pass `brew audit --new-formula <formula>` (after doing `brew install <formula>`)?
+- [ ] Have you followed the [guidelines for contributing](https://github.com/Homebrew/homebrew-core/blob/master/CONTRIBUTING.md)?
+- [ ] Have you checked that there aren't other open [pull requests](https://github.com/Homebrew/homebrew-core/pulls) for the same formula update/change?
+- [ ] Have you built your formula locally with `brew install --build-from-source <formula>`, where `<formula>` is the name of the formula you're submitting?
+- [ ] Does your build pass `brew audit --strict <formula>` (after doing `brew install <formula>`)?
 
 -----

CONTRIBUTING.md

@@ -23,15 +23,15 @@ First time contributing to Homebrew? Read our [Code of Conduct](https://github.c
 
 * read [the Formula Cookbook](https://github.com/Homebrew/brew/blob/master/docs/Formula-Cookbook.md#formula-cookbook) or: `brew create $URL` and make edits
 * `brew install foo`
-* `brew audit --online --strict foo`
+* `brew audit --new-formula foo`
 * `git commit` with message formatted `foo 2.3.4 (new formula)`
 * [open a pull request](https://github.com/Homebrew/brew/blob/master/docs/How-To-Open-a-Homebrew-Pull-Request-(and-get-it-merged).md#how-to-open-a-homebrew-pull-request-and-get-it-merged) and fix any failing tests
 
 ### Contribute a fix to the `foo` formula
 
 * `brew edit foo` and make edits
 * leave the [`bottle`](http://www.rubydoc.info/github/Homebrew/brew/master/Formula#bottle-class_method) as-is
-* `brew install foo`, `brew test foo`, and `brew audit foo`
+* `brew uninstall --force foo`, `brew install --build-from-source foo`, `brew test foo`, and `brew audit foo`
 * `git commit` with message formatted `foo: fix <insert details>`
 * [open a pull request](https://github.com/Homebrew/brew/blob/master/docs/How-To-Open-a-Homebrew-Pull-Request-(and-get-it-merged).md#how-to-open-a-homebrew-pull-request-and-get-it-merged) and fix any failing tests