Validation and defaults for posts

Default values taken from:

http://codex.wordpress.org/Function_Reference/wp_insert_post
Validation and defaults for options
Validation and defaults for terms
Validation and defaults for comments
Validation and defaults for users

This includes the hashing of passwords, so you can do:

	User.create(user_login: 'foo', user_pass: 'plaintext_pass')

...and the password will be hashed before the record is inserted.
Merge pull request #3 from robmiller/validation

Validation and defaults