Gauge Confluence v0.13.2

Exit with non-zero code if plugin errors (#41)

* Allow "exit" as first word of git commit messages

* Exit with non-zero code if plugin errors

This commit causes the Gauge Confluence plugin to exit with a non-zero
exit code if the plugin finds that any specs are not in a valid state
for publishing.  This is true both for dry run mode and "normal" mode.

It is useful for CI/CD as it means that the CI/CD pipeline can use the
exit code (0 for success, not 0 for fail) to pass or fail the build.

So a typical workflow would be to have the plugin run in dry run mode on
feature branches, and to fail the build if the plugin exits with a
non-zero exit code.  Then (once the dry run has succeeded and the change
has been successfully merged to the trunk branch) the pipeline can run
the plugin in normal mode and again pass or fail the build depending on
the exit code.  As the plugin has already passed in dry run mode on the
feature branch, it should in theory always pass on the trunk
branch, which is what we want.

NB Gauge only exits with a non-zero exit code for documentation plugins
which return an error since [v.1.4.1][1].

[1]: https://github.com/getgauge/gauge/releases/tag/v1.4.1

* Bump plugin patch version