Add new {{ date }} variable to README

README.md

 |Title                   |Description|
 |------------------------|-----------|
 |`layout.html`           |The main layout. All page content gets injected into the `{{ contents }}` variable. The title of the page is available in the `{{ page_title }}` variable.|
-|`post.html`             |The template for rendering a single post. Variables available include `{{ title }}` and `{{ body }}`.|
-|`page.html`             |The template for rendering a single page. Variables available include `{{ title }}` and `{{ body }}`.|
+|`post.html`             |The template for rendering a single post. Variables available include `{{ date }}`, `{{ title }}` and `{{ body }}`.|
 |`post_listing.html`     |This template is for the list of posts on the index page. The `{{ post_listing }}` variable contains the result of compiling the `post_listing_item.html` template against each post.|
 |`post_listing_item.html`|This template determines how each post will appear in the main listing. Variables available include `{{ title }}` and `{{ slug }}`.|