Adapt to support ghost 2.0

[FrankV01]

Errors
File: post.hbs
- The {{#author}} block helper should be replaced with {{#primary_author}} or {{#foreach authors}}...{{/foreach}}

File: partials/loop.hbs
- The {{#if author.*}} block helper should be replaced with {{#if primary_author.*}}
    or {{#if authors.[#].*}}
- {{author}} should be replaced with {{authors}}
- Replace the {{author.name}} helper with {{primary_author.name}} or {{authors.[#].name}}
- Replace the {{author.profile_image}} helper with {{primary_author.profile_image}} or {{authors.[#].profile_image}}

File: styles
- The .kg-width-wide CSS class is required to use your theme with 2.0
- The .kg-width-full CSS class is required to use your theme with 2.0
- The .kg-gallery-container CSS class is required to use your theme with 2.0
- The .kg-gallery-row CSS class is required to use your theme with 2.0
- The .kg-gallery-image CSS class is required to use your theme with 2.0