Use svgo ^1.0.0

[lencioni]

svgo is on 1.0.3 now, so let's get on a newer version.

I'm not sure if there is anything else needed for this change.

https://github.com/svg/svgo/releases/tag/v1.0.0

[Trainbird]

[email protected] was promisfied (with this commit). Meaning, svgo.optimize(..) now returns a promise instead of using callbacks like it did before. That breaks the plugin, because src/optimize.js:59 uses the old function declaration. It's easily reproducible by running the test script npm run sanity.

I tried to fix it myself, but I have no idea about babel plugins. After some digging and fiddling around I found out, that babel is fully synchronous and there is only some weird hackish looking solutions (at least for me) to get asynchronous code to work (see StackOverflow).

But as for this pull request, @lencioni: Sadly, it needs more to work properly.