Support improvements to exception messages and printing

[mfikes]

Some revisions are landing on ClojureScript master, for which Figwheel can be updated to support.

See CLJS-2913 and CLJS-3011

Also see https://gist.github.com/mfikes/cca647f962f38edb599596f8e7bffc43 for examples of what the new reporting looks like.

[bhauman]

Cool I'll keep an I on this. BTW github has stopped sending me email notifications for my figwheel repos which is a pain.