FF 57 support

[spanevin]

It doesn't work in FireFox Quantum (57.0)

[rugk]

Hint: Needs to be converted into a WebExtension...

[mirkoperillo]

If think this project is not more maintained (last commit is dated October 2016).
If @nathan-osman doesn't confute my words, I suggest to move to other actively mainteined addons.
Some example are:

• Resting
• Rested
• Rester

[rugk]

If so, @nathan-osman should archive this repository, to mark it as unmaintained. People then cannot submit PRs and there is a big warning that this is archived.
Remember to add a note to the Readme before to explain that it is unmaintained, and – if you think this is useful – why and probably mention alternatives.