Added hierarchy.txt to .gitignore
Added support for ancestry resolution to GeoName with methods to derive an ancestry key (<COUNTRY>.<ADM1>.<ADM2>.<ADM3>.<ADM4>), set parents, and determine if a GeoName's ancestry has been fully resolved.  Moved valid GeoName parsing tests into separate methods instead of one massive test case with asserts for different conditions.  Added tests for the ancestry methods.