Add the ability to toggle features on/off

[rviscomi]

Some features like static head evaluation seem to have buggy edge cases (#31). Other features like validation might not be useful to all users. Create a way for users to enable/disable features or customize the script in some ways.

Features:

• static/dynamic head
• validation
• automatically log on page load (extension)
• validation error count badge (extension)

Customizations:

• color palette

capo-pink.mov