Merge pull request #98 from nathanmesserbbc/add_drop_on_error

Adding ability to retain a stale value when generate function fails
Cleanup for #98
Remove getOrGenerate(). Closes #99
Require generateFunc for stale. Closes #100
Consistent policy.get() callback. Closes #101
Use joi. Closes #102
Ignore hapi config. Closes #103
Fix tests. Closes #104
Merge pull request #2 from hapijs/master

Updating from hapjis