When cdn is down specially in the country like china
and others user face problem as application doesn't
work as intended. Instead of making mathjax hard
dependecy I have converted it into soft dependey
so that it won't cause user problem to use application
smothly if mathjax is not present.
TNL-1498
When mathjax is down discussion forum doesn't work
as we were using markdown.js with processor as
mathjax. Unavailability of mathjax raise error in
js which stops discussion to render. So I made
markdown independent of mathjax. Markdown now will
use mathjax when it is available otherwise ignore it.
TNL-1149
