Adds Kosovo

Adds XK = Kosov to the list
Merge pull request #14 from IATI/kosovo-addition

Adds Kosovo
[#17] Add description to country list

This explains that IATI lists some user assigned codes in the XA - XZ
range (currently just XK - Kosovo)
Merge pull request #18 from IATI/17-country-description

[#17] Add description to country list
[IATI/IATI-Codelists#31] Update FlowType based on the latest DAC Spreadsheet

http://www.oecd.org/dac/stats/documentupload/Codelist10072014.xls
Merge branch 'master' into dev