Add PostsController actions 'index', 'new' and 'create'

 * Also defined 'post_params' which controlls params that are acceptable
 input from the outside.
Create 'new' and 'index' views as well as '_form' partial.

 * These are all .haml files. I'm using this project as a step toward
 integrating Haml in my dev workflow.
 * All these files are found in the app/views/posts directory.
Add 'author' column to Posts db table. Migrate database.

 * Create new migration: xxx_add_author_to_posts.rb
 * Migrate db and update db/schema.rb
Add Rails.logger.debug [some-content] to 'new' and 'index' views and
"_form" partial.
Update 'edit' action in PostsController. Edit 'update' action in
PostsController

 * Both are functional now.
Create the 'edit.html.haml' view file. Edit the Rails.logger messages.

 * The logger.debug messages (in my 'view' and '_form' files) were
 preceded by '=' which shows (on the rendered webpage) the result of
 the ruby code. Wherever I made the Rails.logger call, the text 'true'
 was rendered on the webpage.
 - Changing '=' to '-' in each of the view (and partial) files allows
   the code to be processed but there is no text rendered on the page.
Add option to delete a post.

 * Update 'destroy' action in PostsController.
 * Add two links to edit.html.haml view file:
  - Add 'Ignore Edits, Return to Post List
  - Add 'Delete Post'
Add "Don't Create Post, Return to List" path to new.html.haml