Changed
* `FirefoxVersion` was moved from `mozilla_version.firefox` to `mozilla_version.gecko`
* `FirefoxVersion()` doesn't parse strings anymore. `FirefoxVersion.parse(string)` should be called instead.
* `FirefoxVersion()` allows to build version numbers by specifying raw values directly
Added
* In `mozilla_version.gecko`: `ThunderbirdVersion`, `FennecVersion`, `DeveditionVersion`, and `GeckoVersion`. The latter being a class that has generic support of the others (+ `FirefoxVersion`)
* Known edge cases that were ever shipped to Balrog. For instance: Firefox 38.0.5b1.