Adding support for google analytics code; alternate commenting system; option to use image both as cover and as embedded in post

[maricris-sn]

• new partial for analytics code (with comments as guide)
• insert analytics within head tag

[damianmuti]

Have to try this out before merging. Thanks, @maricris-sn !

[maricris-sn]

No worries. @damianmuti. Thanks!