Added to retrieve using value attribute, fallback.

Added an extra if loop to retrieve description values from sites like New York Times who have malformed it by using value instead of content. See http://www.nytimes.com/2012/06/13/world/middleeast/violence-in-syria-continues-as-protesters-killed.html for an example of this bad code.

Also adapted code from https://github.com/bashofmann to create an easy fallback from pages without og tags to pull the title and description meta tags instead.