Sanity check `/pager me N`, in case it's accidentally used to ack/resolve something

[technicalpickles]

We've seen times when someone goes like:

hubot pager sup
hubot pager me 1234

... while attempting to acknowledge the 1234 incident. Instead, this adds a schedule override for the user for 1234 minutes. Incident numbers are much higher, which could lead to several weeks of schedule being override. This could be particularly disasterous if multiple groups are within the PagerDuty account, without overlap in skill sets.

Some fixes might include:

• check if N is an open incident, and warn that they need to ack/resolve it
• if N > X, then ask for a confirmation
• if user is not on the configured schedule, ask for confirmation