Add the new body classes

closes #1967

- adds paged to eventually replace archive-template
- adds page-template to eventually replace page
- changes custom page template class to be page-slug instead of
  page-template-slug
`grunt dev` calls default task

Closes #3942
`js-` prefix; fix content preview back button

Closes #1990, Ref #3810
- Add `js-` prefix to jQuery calls throughout code and templates
- move MarkdownComponent classNames to template
- Fix back button on posts content preview
- Remove dead code for preview tabbing jQuery
Merge pull request #3946 from novaugust/grunt-dev-assets#3942

`grunt dev` runs default task
Smarter `buildAboutPage` task

No issue
- Only run the buildAboutPage task if the `-contributors.hbs` template doesn't exist,
- ... or if the `--force` option is supplied on the CLI
- Adds the contributors img dir and the contributors template to `grunt clean:built` task
Merge pull request #3949 from novaugust/js-prefixes

`js-` prefix codebase; fix content preview back button
Merge pull request #3852 from ErisDS/issue-1967

Add the new body classes
Show settings-cog and back button

closes #3925
- Make user-settings-cog reappear
- Show [< Users] back button
Merge pull request #3944 from halfdan/3925-cog-back

Show settings-cog and back button
Merge pull request #3945 from novaugust/smart-contributors

Smarter `buildAboutPage` task
Apply JSHint to test files.

closes #2666
- Add new jshint:test task
- Fix jshint errors
Merge pull request #3953 from halfdan/2666-jshint-test

Apply JSHint to test files.