Add JReq job application resume-checking specs.

Add specs to check whether jobseekers must include a resume when applying to a JReq-type job.
Fulfill JReq resume-checking specs.

Fulfill specs confirming that jobseekers must supply a resume when applying to JReq-type jobs.

Add JobType class.

Add Job#suitable_resume?.

Make NoResume a singleton instead of an instantiated object.