Add browser script option to package.json

This will tell any browserify project to package the browser version of
mocha and not the Node version.

Fixes issue #880

This will only cover the JavaScript packaging, CSS is still done
manually through <link> tags.
Merge pull request #1197 from sukima/feature/add-browser-directive

Add browser script option to package.json
small tweak to clean() to show failure deatils

In json output, there was no detail shown for the failures.  Adding line #69 results in failed tests showing the 'err' object.
removing ' || undefined'
"Merge pull request #1205 from ben-bradley/patch-1\n\nsmall tweak to clean() to show failure deatils"

* ben-bradley/patch-1:
  removing ' || undefined'
  small tweak to clean() to show failure deatils
Fix style (#1205)
Add docs for wrapped node flags in mocha --help