Add instagram support

[PatMyron]

With jQuery enabled,

$('._owark').remove();

currently gets rid of the Instagram feed for me. However, I'm not sure if this classname changes over time.

[jordwest]

This should be possible in future once we've sorted out the permissions issue (#50)

[PatMyron]

Didn't realize Chrome extensions had programmatic permission requests in addition to manifest defined permissions. Google moved Android towards that model as well a bit ago. Let me know if you want any help with the code. This could be useful for even more sites like Twitter, LinkedIn, etc as well.

[PatMyron]

$('.stream').remove(); Twitter
$('#siteTable').remove(); Reddit
$('.news').remove(); Github
$('#mainbar').remove(); Stackoverflow (also removes content on specific question pages)
$('.layout_3col_center').remove(); Quora
$('#pageContent, .copilot-secure-display').remove(); Amazon
$('.posts').remove(); Tumblr
$('.gridCentered').remove(); Pinterest
$('.core-rail').remove(); Linkedin
$('.relative').remove(); Linkedin (looks better, but items come back if you scroll after)

[jordwest]

Merging this into #63