Document running standalone

Fixes #32

Author: Mike Foley

Diff for: README.md

@@ -164,6 +164,17 @@ Fit Commit aims to enforce *community standards*. The two influential guides are
 
 The Git community has largely (but not completely) coalesced around these standards. [Chris Beams](http://chris.beams.io/posts/git-commit/) and the [Pro Git book](https://git-scm.com/book) also provide good summaries on why we have them.
 
+### How can I run this standalone, like part of a CI process?
+
+Fit Commit can be run outside of a Git hook context with a simple shell script:
+
+```sh
+$ GIT_BRANCH_NAME=branch_name COMMIT_MESSAGE_PATH=path/to/message rbenv exec ruby -rrubygems -e 'require "fit_commit"; FitCommit.run'
+```
+
+It exits with an error code if any errors are present, which will fail a build if it's part of a CI run. The configuration should be modified for CI to be more lenient, otherwise false positives will break the build too often.
+
+
 ### How can I improve Fit Commit?
 Fit Commit aims to be useful to everyone. If you can suggest an improvement to make it useful to more people, please open a GitHub Issue or Pull Request. See [CONTRIBUTING.md](CONTRIBUTING.md) for more info.