Implemented caching in jake

Changes made to this project:

Initial responses from OSSIndex are cached for 12 hours
Subsequent requests are checked against the cache, if a hit is found it's checked to see if it's less than 12 hours old, if it is, we grab the response and insert it and discard that purl for checking against OSSIndex. After the 12-hours ttl, we will readd purls to the request, and then insert those responses into the cache.

THERE ARE ONLY TWO HARD PROBLEMS IN COMPUTER SCIENCE. CACHE INVALIDATION, NAMING THINGS, AND OFF BY ONE ERRORS.

We also added a -C to jake to allow you to clean the cache if desired

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sonatype-nexus-community / jake