Configure dependencies and notifications

*(resubmission of [pull request 14](https://github.com/puppetlabs/puppetlabs-passenger/pull/14))*

This fixes 2 issues.

1. It prevents enabling the module if the compilation failed. Otherwise if compilation fails, apache will generate an error when it tries to start and the binary doesn't exist.

2. Sets up notifications so that if the config is updated, apache reloads.