Use .tsv extension for cached Florida files
Use .tsv extension for cached Florida files

The files are tab-delimited, so make this clear from the extension.
This also makes it easier to open files by clicking on them.

Closes #88

openelections/openelections-core,cathydeng/openelections-core,datamade/openelections-core,openelections/openelections-core,cathydeng/openelections-core,datamade/openelections-core