Allow themes to provide custom error template.

fixes #1212, #1213
adds prefix option to tag helper

        closes #607

 - added prefix attributetor tags helper
 - will add prefix only if tags are present
 - adds unit tests for prefix
Merge pull request #1218 from halfdan/1212-themable-error-pages

Allow themes to provide custom error template.
Merge pull request #1239 from cobbspur/tagsprefix

adds prefix option to tag helper
Replace nodejs-bcrypt with bcryptjs

* https://github.com/shaneGirish/bcrypt-nodejs
* https://github.com/dcodeIO/bcrypt.js
Merge pull request #1248 from halfdan/bcryptjs

Replace nodejs-bcrypt with bcryptjs
Add validation for importer

closes #952
- moved api.js to api/index.js
- added api/db.js for import and export functions
- moved /ghost/debug/db/export to GET /api/v0.1/db
- moved /ghost/debug/db/import to POST /api/v0.1/db
- removed /ghost/debug/db/reset
- added validation for import
- added constraints object to migration
Merge pull request #986 from sebgie/issue#952
Fixed style of modal in preview.

fixes #1179
Merge pull request #1202 from halfdan/1179-modal-styles
Explicitly add Ruby dependencies to project via Bundler

closes #1220
- This uses Bundler to install Ruby dependencies to handle explicit
  dependencies in provisioned environments
- The initial Gemfile contains SASS dependencies (sass and bourbon gems)
State that Bourbon files are generated in CONTRIBUTING guide

Fixes #1255.
- This says that the Bourbon directory is generated and does not
  ambiguiate with the installation of the bourbon gem
Only show notifications when logged in.

fixes #943
Merge pull request #1256 from mduvall/contributing-fix-for-bourbon

State that Bourbon files are generated in CONTRIBUTING guide
Merge pull request #1220 from mduvall/ruby-dependencies

Explicitly add Ruby dependencies to project
Merge pull request #1254 from halfdan/943-login-notification

Only show notifications when logged in.
Move /api to /ghost/api

closes #1249
- changed routes
- changed apiRoots