Add Instapaper support.

[darron]

I use Instapaper to read long form items later - this is a pretty small addition - let me know if you're interested in merging it.

[robsalasco]

I use pocket! can you add support please :)?

[swanson]

Hi - I won't be adding any bookmarking/social sharing stuff to master at this time.

Feel free to keep this in your branch; the code looks good, but it does not align with the current vision for the project.

Thanks!

[bitboxer]

I totally understand your vision for the project. But for people who want those features, I started a small chrome extension 😉

https://github.com/bitboxer/chrome-stringer-socialize

[fuadsaud]

stringer is totally anti-social, man! :)

I'm kidding, nice extension, btw, @bitboxer.