Added `initial` for legacy `flex` support
Made `size` also accept the `auto` and `initial` values
Added tests for `size` with `auto` and `initial` values
Added `tab-size`
Introduced the `initial-*` variables, to be used by `reset` and `normalize`
Made `normalize` aware of the `initial-*` values
Introduced the `initial-*` variables, to be used by `reset` and `normalize`
Made `normalize` aware of the `initial-*` values
Merge branch 'master' into issue-4-reset
Made `reset` aware of the `initial-*` variables