[EM] Block group map of Texas

[Raph Frank]

I also added blocks for Maine.

http://www.electionsciencefoundation.com/temp_images/maine_blocks.zip

There are "island" blocks which are completely surrounded by other blocks.

It is probably worth scanning for them and designating them part of
the block that they are enclosed by.  Unless they have a population
greater than a district, it is not possible for them to be placed in a
different district to their "parent" block.