Change validation for posts 'page' attribute.

issue #2305
- changed validation for 'page' to expect '0' or '1', rather than 'true' or
  'false'
- Added a 'can change a post to static page' test
- Added a 'can change a static page to a post' test
Fixing CodeMirror paths in GruntFile.js
Detect tag.hbs template in themes

closes #2320
- changed detection from "tag" to "tag.hbs" in "frontend.js" contrroller
Add test for tag.hbs template.

refs #2321
Bower dependency order OCD
Do not cache 404 pages

closes #2334

- remove call to set cache-control in 404 response header
- update unit tests to expect this
Merge branch 'nocache404' of https://github.com/dsschnau/Ghost into nocache404