Add Media Queries support, and re-introduce the one-whole width.

https://github.com/inuitcss/trumps.widths/pull/2 needs to be merged first.

**Media Queries support:**
* It take the `media-query` mixin from Inuit v5 as a reference.
* It still generate an elegant CSS code: all selectors which have the same width property are merged together (thanks to the new `map` data-type), and the mixin adds a comment block before each group of proportions.
* It keep the philosophy of the modular architecture. For example: if the `media-query` mixin is not available (detected via the new `mixin-exists` function), it will warn the user.

**`one-whole`/`1-whole` width:**
* I used the `_trumps.width` in my latest project, and the `1-whole` was still necessary, particularly for some specific breakpoints.

If I have some time soon, I will play a bit with the pull & push helpers. I will submit a Gist for that (because this will be probably a new independent module).