Growl style desktop notifications

First pass. See #1349
Moved getting involved section
Clearer contribution guidelines
Merge pull request #1440 from JohnONolan/post-settings

Post settings refactor
Merge pull request #1442 from Decad/user-gravatar

Add users Gravatar on signup
Merge pull request #1446 from JohnONolan/notifications

Growl style desktop notifications
Add support for SVG images
Move plugin init code into plugin.js and have it called from server.js
Update CONTRIBUTING.md
Merge pull request #1462 from hswolff/plugin-init-cleanup

Move plugin init code into plugin.js and have it called from server.js
Merge pull request #1458 from mjbshaw/svg

Add support for SVG images
Pass proxy Ghost interface to Apps

Closes #1478

- Create new proxy.js that exposes createProxy method
- Pass proxy to App activate/install in lieu of Ghost instance
Adding recommended fields to package.json
Fix wrong error message

closes #1466
- added status code for error object
- added test for frontend errors
Remove inline script from default.hbs

closes #1268
Lowercase email address.

fixes #1498
Add schema.js

closes #1398
closes #1399
closes #1400
- added schema.js with database version '000'
- refactored migration to use schema.js
- if new table is added to schema.js and databaseVersion is increased, table will be added
- if new table is deleted to schema.js and databaseVersion is increased, table will be deleted
- alter table from issue #1400 is delayed until knex supports column modification
- changed import pre checks to work again (will be refactored separately)
- added basic PostgreSQL support (Attention: not supported/tested)
- changed error handling in server.js
Merge pull request #1489 from sebgie/issue#1466

Fix wrong error message
Merge pull request #1505 from halfdan/1498-lower-email

Lowercase email address.
Merge pull request #1353 from thgaskell/1350-static-page-checkbox

Allow user to set static page before saving