Fix opengraph img tag
Add some more og:image to choose from
Microdata & canonical url attached.

Reference: http://www.lrmi.net/the-specification/examples
"No course micro data currently availble" : https://groups.google.com/forum/#!topic/lrmi/KLxe5i_1uTY
Fixup the micro data
Add GA events for clicks on the engagement button
Merge pull request #1 from NTU-CCSP/feature/seo

Open graph tags, microdata and canonical URL.