Version history
===============
1.0 (June 20, 2013):  Initial release.
1.1 (February 15, 2014): Added districts of the 113th Congress (shapes from the US census).
1.2 (March 20, 2015): Fixed error in Washington's first district in the 91st and 92nd Congress.
1.3 (May 30, 2016): Added 114th Congress.  Clipped 113th and 114th to land to match earlier shapes.