Make into WebExtension compatible with Firefox

[joallard]

Follows comments on #168

[phoebejaffe]

I'm happy to merge this. I'll release the chrome update sometime this weekend, possibly next week (things are a bit hectic), but since it's a small styling change, a slower release shouldn't be a big deal.

@joallard, any other things you're working on for this PR, or is it good to go?

[joallard]

I was trying to remove the dependency on Bower, but I'm not that well versed in js to know what the good practices are in 2017. I had a WIP locally, I'll try to add that and we'll be good to go.

[brenthaas]

Any progress on this? I'm looking to contribute as well, and it would be nice to not have the bower dependency if possible

[joallard]

While I agree, I'll leave Bower out of scope for this PR as it pretty much gums up the works. Expect an update to this PR along with a final LGTM. Soon.

[instantgreen]

Any progress?

Since Firefox Quantum got released a few days back I looked into installing this addon through Foxified. The addon tries to upload the okc-plugin to Mozilla but it got rejected due to several problems.

This means I still would like to see this issue be successful...