* preset-env: minimally supporting version
This changes the "does browser support X" algorithm to "lowest version such that all higher versions support it".
Eg, given `{ chrome70: true, chrome60: false, chrome50: true }`, the lowest version is chrome70, not chrome50.
This is done to remove Tagged Template Literal support from Safari, which introduced a bug in Safari 12 but correctly implemented the feature in Safari 11-9.
* Add tests
* Fix tests
* Fix comment
Likely because of implicit `equals` (ie, Safari 12 support implies iOS Safari 12), the versions in the `res` hash are not always sorted in version order.
Doing a semver sort reveals some builtins have actually been supported a little longer than we thought!
