Take row with largest year/timestamp
Merge branch 'master' into feature/281
Fix tests so they don't call `done` multiple times
If no result, return `null` instead of `undefined`.
Add `exactyear` flag for getEntry. If truthy, only accepts that year.

Only used for tests.
Add a test confirming that if two entries are added, the one for the later year is chosen.
Merge pull request #306 from okfn/feature/281

Show previous years from `display_year`