Cachet-url-monitor

Adding the ability to scrape a CachetHQ instance to automatically produce a configuration file.

Improving expectation validation from the configuration file.

Now cachet-url-monitor supports multiple URLs under the same instance (66) thanks to aberenshtein implementation.

Adding the ability to override the incident status for each `expectation`. Feature request (72)

1. Changed docker command to `CMD`
2. Adding ability to create incidents when a check fails.
3. Verifying component status upon initialization.
4. Allowing override configuration through environment variables.
5. Refactored status to another file for better importing it (thanks rahulg963)
6. Documentation fixes (thanks gardner)
7. Refactored status and incident update to be optional and complementary (initial implementation by jacekszubert)