Tweaking slug logic in post settings.

Closes #2136.
- sets slug to placeholder text if slug is blank
Adds ability to pass in configFile path when loading 
 ghost as a npm module

- modifies main script file to allow it to
take in an options object that currently
supports an express instance or a config file path

- added tests
Allow HTML inside tag prefix/suffix

closes #2123
- Return hbs.Safestring
- Manually escape joined tags
- Added test
Merge pull request #2151 from halfdan/2123-tags-suffix

Allow HTML inside tag prefix/suffix
Merge pull request #2147 from gmurphey/master

Tweaking slug logic in post settings.
Merge pull request #1818 from hswolff/config-file-option

Adds ability to pass in configFile path when loading ghost as a npm module
Install App Dependencies

- Spawns an npm install command from the App root
- Has some special OS checks for windows command spawning
Merge pull request #2099 from jgable/appDependencies

Install App Dependencies