Change HTML email link to hide token

closes #3305
- Hide token in HTML email
Naming cleanup

closes #4069
- Rename everything from camelCase to lowercase + dashes
- Remove usage of `server`, `app` and `instance`
Meta data screen

closes #3939
- Add Seo Tab component to PSM
- Add new gh-blur-textarea component
- Refactor blur-input to use new text-input mixin
Merge pull request #4066 from halfdan/3939-psm3-meta

Meta data screen
Add Gmail-style shortcuts

Ref #3940
- add `j`/`k` for navigating posts down / up
- `c` for opening a new post
-  `o` to open the selected post
- update keymaster dep to allow for multiple key unbinds (`key.unbind('up, j')`)
Fixes sass:compress

no ref
- Use absolute path for compress/sourceMap
Merge pull request #4092 from halfdan/fix-sass

Fixes sass:compress
Merge pull request #4081 from halfdan/3305-derp

Change HTML email link to hide token
Validate and properly color letter count.

fixes #4087
- Adds correct validations for meta_title/meta_description
- Adds correct coloring of letter count
Fix minor IE UI issues

Closes #4088

- Fix Flexbox issue with the user list
- Fix positioning issue with the mobile menu toggle icon
- Make the mobile settings nav use absolute positioning (as fixed elements don't move inside a `transform: translate(...);` parent
Show all authors in post settings menu

Closes #4016
- Added 'limit=all' to API query to retrieve all users.
{{gh-path}} Handlebars helper, returning paths

- Uses utils/ghost-paths to resolve paths
- {{gh-path}} or {{gh-path ‘blog’}} for Ghost’s root (mysubdir/)
- {{gh-path ‘admin’}} for Ghost’s admin root (/mysubdir/ghost)
- {{gh-path ‘api’}} for Ghost’s admin root (/mysubdir/ghost/api/v0.1)
Merge pull request #4074 from halfdan/4069-rename

Naming cleanup
Add checks for packages and contentPath to startup

Refs #3864
- Make sure that require() is able to resolve all dependencies
  listed in package.json.  If packages are missing halt the
  bootstrap process and display an error and help message for user.
- Check that contentPath and its subdirectories exist with the correct
  permissions.
- Check sqlite3 database file is set for read/write access.
Merge pull request #4094 from frantzypants/issue-4016

Show all authors in post settings menu
Merge pull request #4089 from halfdan/4087-meta

Validate and properly color letter count.
Merge pull request #3913 from jaswilli/require-errors

Add checks for packages and contentPath to startup
Fix uncentered no posts view

Closes #4097
Merge pull request #4100 from novaugust/iss4097

Fix uncentered no posts view
Merge pull request #4090 from PaulAdamDavis/ie-fixes

IE UI fixes