Add interactive command to create new incident.

[calavera]

- Do you want to request a feature or report a bug?

This is a new feature.

- What is the current behavior?

You need to use hugo directly to create a new incident and then modify the frontMatter.

- What is the expected behavior?

I'd like to type something like npm run new and then be prompted with a series of questions, something like this:

prompt> npm run new
output > What the cause of the incident? 
input   > Connection issues in the load balancer
output > What's the severity of the incident? (degraded-performance, minor-outage, major-outage...)
input   >  minor-outage
output > What are the affected systems? (API, CDN, Origin servers...)
input   > CDN, Origin servers
output > Edit site/content/incidents/connection-issues-in-the-load-balancer.md ? (y/n)
input   > n
prompt>

The last question is not required, but having a prompt like this would make the process slightly faster and more convenient, specially to fill severity and affected systems.

[AmGarera]

I'd like to take a shot at this in the upcoming week when my time frees up

[steveoh]

FYI, I started this with #28

[steveoh]

this can be closed also.