Removing docs task from test, test-browserify and coverage build chain

As mentioned in #799, an extra directory is being created upon `grunt test`. This directory, web/docs/public, is being created as part of the grunt-docco2 task. 

It seems misplaced to me to have to build the docs during a test run. I don't think a user running `grunt test` expects the docs to be built during this phase of the build lifecycle. IMO, an appropriate place to build the docs is during the `grunt build` task.