[FEATURE] Check for newer version of Jake during startup

[bhamail]

• What are you trying to do? When Jake runs, it should check to see if a newer version of Jake has been released. If a new release exists, prompt the user to upgrade to the latest release. The prompt should include a command to perform the upgrade, e.g. pip install jake --upgrade

some learnings from similar efforts:

• provide a way to bypass the check (via CLI flag). see: https://github.com/sonatype-nexus-community/nancy/issues/217 and https://github.com/sonatype-nexus-community/nancy/pull/218 The ability to skip the check when a given ENV VAR is set is also useful in CI systems.
• cache the date/time when the last check was performed, and only check again in say 28 hours.
• also include the command to perform the upgrade in the application help (and maybe the README.md?).

cc @bhamail / @DarthHater