Closes #17. Adds acquisitionYear to JSON and CSV. Removes workCounts …

…and artistCounts from JSON files to prevent arbitrarily large changesets. Each release of data should now give a more accurate account of significant changes.

v1.1 2013-12-20 Latest data update. Includes artist role, better dime…

…nsion parsing, missing artist.

Publicly announced release of Tate data.