Refactor require-tree to not share messages

- Pass in messages to each method so they are not shared
- Export each method for calling individually
- Update reference to default export of require-tree
- Add default values for messages if not passed in
Prevent settings page from rendering same page twice

Closes #2316
- There was a check to prevent rerendering of same content pane but it wasn't working
- Fixed the check for this
Use tag as title on tag pages

closes #2328
- added check for tag in coreHelpers.meta_title and use if set
- added test for correct title on tag pages

Rewritting to tag - blogtitle based on comments from PR
Merge pull request #2329 from stenehall/master

Fix for #2328 - Added check for tag for title
Merge pull request #2317 from shashankmehta/settings-rendering-issue

Prevent settings page from rendering same page twice
Merge pull request #2292 from jgable/requireTree

Refactor require-tree to not share messages and export parsePackageJson
Replace JSLint with JSHint.

closes #2277
- Added ES6 linting to core/client/
- Fix typeof array comparison