Avatar functionality to membership card

[andrewlimaza]

• ENHANCEMENT: Add the ability to show_avatar attribute to show the members avatar.

• ENHANCEMENT: New filter added to give you even more control over the avatar settings - pmpro_membership_card_avatar_args (takes an array of values that passes through to the get_avatar function).

All Submissions:

• Have you followed the Contributing guidelines?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Resolves 19.

How to test the changes in this Pull Request:

1. Try the shortcode [pmpro_membership_card show_avatar="true"]

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully run tests with your changes locally?

[andrewlimaza]

Example of the avatar showing. The filter gives you full control over what is passed to get_avatar to tweak it even further.